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Kundu H.L.-Ecology for Millions

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NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS
PUBLISHING FOR ONE WORLD
New Delhi · Bangalore · Chennai · Cochin · Guwahati · Hyderabad
Jalandhar · Kolkata · Lucknow · Mumbai · Ranchi
Visit us at www.newagepublishers.com
Copyright © 2006 New Age International (P) Ltd., Publishers
Published by New Age International (P) Ltd., Publishers
All rights reserved.
No part of this ebook may be reproduced in any form, by photostat, microfilm,
xerography, or any other means, or incorporated into any information retrieval
system, electronic or mechanical, without the written permission of the publisher.
All inquiries should be emailed to rights@newagepublishers.com
ISBN : 978-81-224-2433-1
PUBLISHING FOR ONE WORLD
NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS
4835/24, Ansari Road, Daryaganj, New Delhi - 110002
Visit us at www.newagepublishers.com
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Introduction
5
PREFACE
Ecology teaches us, how to lead a healthy and progressive life, while living in harmony with nature.
In many countries however, despite its extreme relevance, Ecology is understood by very few. Lack
of this understanding has resulted in many ills in such countries, particularly, impoverishment in the
quality of lives of their citizens, as well as the environment they live in.
This book is a humble attempt to take the basic concepts of Ecology to the common man.
Because it is the common man and woman who matter, as it is they who by their intelligent or
unintelligent acts can make or mar the environment they live in. Much of the future happiness of
mankind is hinged upon man’s use of his environment.
Since the target population of this book is the common man I have deliberately avoided
technicalities to explain the various concepts. Also my teaching experience of something over three
decades in an University regarding Ecology has convinced me that the basic Ecological principles can
be explained without the use of technical jargon.
The book is presented in ten small Chapters arranged in conceptual sequence. For interested
readers, however, information regarding technical literature is given at appropriate places.
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6
Ecology for Millions
ACKNOWLEDGEMENT
Although the seed of desire to wite such a book had lain dormant in me for years, I am not sure if
this book would have ever seen the light of the day but for the encouragement which I received from
certain people. First and foremost, Sadhana, my wife and life partner of forty years for her
unrelenting support. Next come two very special friends, Professor RR Gulati for his persistent
goading and faith which kept me going during all the years of toil and tribulations and Dr Vinod Jain
whose friendly and forthright discussions helped shape the aim of this book; and also my children and
their spouses, Sanghmitra and Suresh and Subroto and Shamita for their diligent search for relevant
data, manuscript corrections and many useful suggestions. Last but not the least I would like to thank
my father, the late Professor Surendra Lal Kundu and my brother, the late Mr J L Kundu who shaped
my character and attitude.
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Introduction
7
CONTENTS
Preface
Acknowledgement
1. Introduction
v
vii
1
2. The Ecosystem
15
3. Productivity
33
4. Bioenergetics
65
5. Bio-Geo Cycles of Chemicals
83
6. Populations
103
7. Community
149
8. Biomes
173
9. Pollution
219
10. Problems and Solutions
Bibliography
241
280
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Introduction
1
Chapter I
Introduction
(The Beginning)
Topics
I.1. History and meaning of the word Ecology
I.2. Ecological Consciousness in Ancient World
I.3. Renaissance and Anthropocentrism
I.4. Rebirth of Ecology and Its Multidisciplinary Nature
I.5. Aim of This Book
I.6. A Bird’s Eye View of This Book
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Introduction
3
CHAPTER I
INTRODUCTION
(The Beginning)
1. HISTORY AND MEANING OF THE WORD ECOLOGY
1.1. Soon after Charles Darwin wrote his revolutionary book, “The Origin
of Species” in 1859, ecological thoughts began to hover upon the minds
of biologists. In 1870 German biologist Ernst Haeckel coined the word
Oekologie using two Greek words oikos meaning “home” and logos
meaning “science”. From Oekologie arose the word Ecology and it was
first used in 1892.
The Beginning
1.2. Briefly, Ecology is that branch of biology which deals with the
interactions between various living beings and their environments. Or
more simply, Ecology is the art which shows us how to live in harmony
with Nature.
1.3. The general concept of ecology however, is not post-Darwinian but
definitely pre-Darwinian. While voyaging round the world in H.M.S.
Beagle from 1827-31, Darwin was much taken by the glowing accounts
tropical scenery of the Amazon river valley of South America by a much
earlier German naturalist traveller Alexander von Humboldt (1769-1859).
Like Humboldt, Darwin too was much struck with the varieties of animals
and plants of different countries visited by him during this voyage.
1.4. So one can fairly say that Alexander von Humboldt laid the seeds of
modern ecology in the minds of biologists. Humboldt’s book “Personal
Narrative” & Darwin’s book “The Origin of Species” (1859) are classics
of Natural History. These surely can be looked upon as the starting points
of today's ecology.
1.5. Since Humboldt, Darwin and Haeckel, all over Europe and North
America many ecological studies began. Gradually a general meaning of
the word Ecology emerged. Today Ecology means the studies of the
relationships of living beings with their non-living environments and
vice-versa. Naturally ecological processes are complex varying from
species to species and involving several factors according to the
environments they live in. As a matter of fact ecology to-day has become
so important that once a renowned biologist Thiodosius Dobjhansky said,
“Nothing in biology makes sense, except in the light of ecology—that is,
Darwin’s voyage in
H.M.S. Beagle
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Ecology for Millions
in terms of interactions between organisms and their physical, chemical
and biological environments” (Preface—pp. vii. of ECOLOGY by Begon,
Harper & Townsend; Blackwell 1990).
2. ECOLOGICAL CONSCIOUSNESS IN ANCIENT WORLD
2.0. Wise men of the past were very much aware of the importance of
plants and animals although they did not have any specific knowledge
ecology so, they established traditions which when respected would
automatically protect parts of their environment and thus ensure
prosperity to their future generations. Following are a few such examples.
2.1. Ancient Egyptian Customs. In ancient Egypt animals played a very
prominent role in the lives of its people. It is apparent from the paintings
and etchings in the tombs of the Pharaohs. One animal—the jackal was
given the status of God—“Anubis”. Anubis the jackal-god was the
protector to them. Crocodile was another God—the God of Fertility.
There were other gods as well. They were all protected.
2.2. Hindu customs—ancient and present. (a) Cow worship. The
Aryans—predecessors of Hindus who moved into India from Bacteria and
Northern Iran during early second milllenium B.C. (Map - I.1), were
hunters and herdsmen consuming both milk and meat of cows. During
that time beef-eating was so much in vogue that a guest was particularly
entertained by being treated with food prepared by sacrificing a young
cow or calf. (Sanskrit was the language of the early Aryans. So in
sanskrit literature there is a word ‘GOGHNA’ meaning a cow-killer. Thus
a honoured guest was a ‘GOGHNA’. The word ‘GOGHNA’ was used by
the famous sanskrit poet Kalidasa in his book ‘ABHIGYANA
SAKUNTALAM’).
2.2.(a) Origin of Cow-worship amongst Hindus. But in the Gangetic
valley cattle suffered from high humidity resulting in premature death. So
the Aryan scholars aiming to protect the cattle attributed holiness to cows
so that cows would no longer be used as beef. Thus the cow-worship or at
least veneration for cows amongst many Hindus (who are mostly
discendants of Aryans and the local tribes of India who gradually adopted
Aryan Culture, is really socio ecological adaptatian to protect the cows of
India from premature death and thus help their owners (The Continent of
Circe by Nirad C. Chaudhuri, 1966, Jaico, Delhi).
2.2.(b) Bishnois of Rajasthan. In some villages of Rajasthan, India,
there lives a sect of people called Bishnois; Bishnois neither kill nor allow
anybody else to kill an animal—even wild ones, in their village or its vicinity.
Wild animals move very freely in Bishnoi villages. Recently a very popular
filmstar from Bombay went into a forest in Rajasthan, near a Bishnoi village
and shot two ‘nilgais’ (Boselapus tragocamelus; Bovidae;
ARTIODACTYLA ). This enraged local people, Bishnois so much that they
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Introduction
5
60
70
70
20
40
60
100
160
70
60
50
50
40
40
30
30
20
20
10
10
0
0
40
50
60
70
80
90
100
130
Map I.1 Dispersal of Proto-Indo-Iranians from north of Caucasus Mountains
to the Gates of Western India (4th. - 1st. Millennium B.C.)
forced the police to take action against this film-star.
2.2.(c) Feeding ants by Jains. Jains a sect of Hindus who are not
only strict vegetarians they even do not kill insects. Often, in the morning,
they put sugar in front of the ant hills so that the ants can begin the day
with a hearty breakfast!
2.2.(d) No-Fishing Day amongst Bengalee fishermen. During
some specific days in June, fishermen of West Bengal (India), &
Bangladesh would not cast their fishing nets in water so that fishes can
breed uninterrupted and thus ensure abundance of fishes for the future.
2.2.(e) The monkey-god—‘Hanuman’. According to ‘Ramayana’
the famous sanskrit epic, a langur (Semnopithecus entellus, Colibidae.
PRIMATE) named ‘Hanuman’ and his friends helped Rama the hero of
Ramayana to wage war against Ravana and finally defeat him. Since then
140
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Ecology for Millions
to Hindus the monkey god 'Hanuman' has become a most respected god
and hence not killed. In many states of India, particularly Rajasthan there
are numerous small temples dedicated to Hanuman. Also, wherever
possible these temples are erected under a specific local acacia tree—
Prosopis spicigera. These trees are very useful to the locals. The branches
which are lopped before the winter, are used as fuel, and leaves as camel
food. So along with this species of monkey this acacia tree also enjoys
some amount of protection.
2.3. Noah’s Arc and Christian Culture. The account of Noah’s Arc in
Bible is a very nice way of implanting the seeds for respect for animals and
plants in the minds of people. Many excellent works, mostly by Christians,
have now been initiated all over the world to protect wild life and Nature.
2.4. The Mongol Hunt and Ban on Hunting during Breeding Season of
animals. During thirteenth century the great Venetian traveller Marco Polo
travelled all over Asia, including China and India for nearly a quarter
century. He stayed in the court of the of the famous Mongol ruler of China,
Kublai Khan the descendent of Genghis Khan, for seventeen years and left
a very picturesque description of the ways of the Khan’s Court and the
countries he travelled through as Khan's emissary. Mongols were very fond
of hunting. The annual hunting expedition of Kublai Khan consisted of
even 10,000 men and as many as 5000 hounds. (Travels of Marco Polo by
Maria Bellonci; Tr. by Teresa Waugh 1984 pp. 83) A very vivid description
of a Mongol hunt during Genghis Khan's reign is given by Harold Lamb in
his book “Genghis Khan: “Emperor of All Men”. (1927, 57). pp. 137-40.
Nevertheless Mongols very well understood that unless the animals are
allowed to breed uninterrupted during breeding season, their hunts would
not last long. So the Great Kublai Khan decreed that no King or Nobleman
throughout his empire can hunt hare, does, roebuck, stags or such like
animals between the months of May to October as, this is their breeding
season. Anybody violating this decree would be severely punished. So
strictly this decree was observed by the subjects of Khan that even the
animals understood this and hence during these months they would come
near men without fear (Teresa Waugh 1984 vide supra p. 85). It is an irony
of fate that after quarter century, when Marco Palo returned to venice and
told people what he saw, nobody believed him. He ended his life belhind
bars.
2.5. Surely there were and are many more worthy traditions all over the
world which helped to protect the environment amongst the erstwhile and
present communities of the world. An anthology of such traditions
throughout the world would verily form an worthwhile theme of a book.
3. RENAISSANCE AND ANTHROPOCENTRISM
3.1. In the ancient world there existed a reasonable balance between men
and their living environment. But with renaissance all these changed.
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Introduction
7
Renaissance had a dual effect on the course of human history. Men shook
off the shackles of blind orthodoxy and took up reason and experiment as
their guides. This soon led to an explosive growth of knowledge in all
directions. Knowledge of Navigation, Mathematics, Astronomy, Physics,
Chemistry, Natural History, Medicine and many other areas all grew very
fast. Sadly though these people who did all these were, not only men of
keen minds and indomitable courage but of insatiable greed as well. They
not only crisscrossed the earth and discovered new countries (e.g.
Americas, New Zealand and Australia) but soon found out which produce
of Mother Nature—be it from any country—is economically most useful
to them. Soon with the help of firearms and superior discipline in groupactivity, these interpid people mastered the Earth and started a ruthless
exploitation of Nature. They tore open the Earth and began looting her
bounty. Almost the entire earth surface was curved out and distributed
amongst the European nations— the renaissance countries. Never before
Earth was ravished so ruthlessly, so thoroughly and in such a short time.
The trend is still on. Handful of Europeans including Russians, directly or
indirectly, colonised the entire North America, South America, Australia and
New Zealand. The combined area of these Europe-colonised countries
would be 2.11 times of Europe including Russia and Europe minus Russia
15 times (Table I.1).
Anthropocentric
attitude & its
consequence
Table I.1.
AREAS COLONISED BY EUROPEAN
COUNTRIES SINCE RENAISSANCE *
Continents
Countries
Chekoslovakia
France
EUROPE
Germany
Italy
Poland
Russia
Spain
Sweden
U.K.
Areas (Sq. Km.)
78703
547030
356910
301230
312683
17075200
504750
449964
244820
NORTH AMERICA
Canada
Mexico
U.S.A.
9976140
1972550
9629091
SOUTH AMERICA
(Selected countries)
Argentina
Brazil
Nicaragua
Venezuela
2766890
8511065
129494
912050
AUSTRALIA
NEW ZEALAND
Australia
New Zealand
7686850
268680
*Summary by author from C.I.A. data—1997-98.
Total Areas of Continents (Sq. Km.)
(1) Total of Europe including Russia is
19871290
(2) Europe minus Russia is 2796090
21577781
12320399
7955530
Total of these
European colonies is
41853710
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8
Ecology for Millions
3.2. Along with this exploitation of Nature, the growth of knowledge of
modern medicine gave a spurt in the growth of human population. So
since renaissance, human population of the world has grown very fast.
Between 5000 B.C. and 1000 A.D. the growth in human population was
quite slow. But from about 1500 A.D. or so (soon after renaissance) the
rise in human population became spectacular and fearful (Fig. I.1.). This
explosive growth of human population however, is not due to any rise in
human fertility (as is commonly believed ) but mostly owing to drop in
child mortality as a result of modern medical care.
3.3. Gradually the native populations of North America, South America,
Australia & New Zealand were almost decimated or withered away and
replaced by more energetic and demanding people of European stock (The
Oregon Trail Francis Parkman; 1967. Bantam Books pp.298). Other
European colonies in Asia and Africa could not however decimate the native
populations but the control passed on to European hands. Only China and
Japan in Asia remained free of European control. A glance at pages 244/5
of Harper Collins Atlas of World History edited by Geoffrey Barraclough
(1998) will corroborate the above statement. Here is one sentence form the
same. “The late 19th century saw a new imperial outburst of an intensely
competitive kind. In the scramble for territory, resources, markets and
outlets for capital investment, an immense part of the world’s total land area
passed under European control” (p. 245) (Map I.2 ). North & South
America have already passed under European hands (Map I.2).
NEW
STONE
AGE
BRONZE
AGE
MIDDLE AGE
OLD
STONE
AGE
IRON
AGE
5
2000
Bubonic flague
1000
CHRISTAN ERA
BEGINS
Figure I.1 Growth of human population in the past half a million years.
AD
BC
1000
2000
3000
4000
5000
YEARS
(BC/AD)
6000
1
7000
2
8000
HUNTERS
3
AGRICULTURE
BEGINS
4
500,000
POPULATION: BILLIONS OF PEOPLE
6
MODERN AGE
3.4. Thus without perhaps conscious knowledge of the indigenes—native
Americans, Africans, Asiatics and Australians, their lands became gignatic
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Introduction
9
180°
120°
60°
0°
60°
120°
180°
60°
60°
ASIA
30°
30°
AFRICA
0°
0°
30°
30°
180°
120°
60°
0°
60°
120°
180°
Map I.2 & 1.3 Growth of European Colonial Empires into different parts of the world (1535 – 1914)
hosepipes through which riches from these countries were sucked into
Europe to provide the Europeans with unprecedented grandeur and comfort
which is now termed as ‘quality of life’. Save China, Japan and middle East
there were perhaps no big country which could resist the canons and
economic exploitation of Europe. So the inevitable happened. Gradually the
natives of these colonies sank into a morass of poverty and ignorance. Both
their wealth and population dropped and their cultures lost their vigour
while the Europeans became richer and their populations rose very fast.
3.5. Before coming to the end of this topic we shall only cite two
examples of exploitation of the same resource one pre-renaissance and
another post-renaissance. According to the renowned Venetian traveller
Marco Polo of 13th century, the island of Scotora in the mouth of Gulf
of Aden was a great whaling centre. Large quantities of ambergis—a
whale product was sold here. Whalers then used to kill sperm whales and
other large whales by using tuna fish as baits and then hrapooning these
by tying ropes with the harpoons. This method of whaling for centuries
however, did not endanger the species but within the last few hundred
years of so, when the harpooners used explosive tipped harpoons and
huge factory ships with their pod of whaling boats so that they can whale
non stop for mouths while roaming all the seas including the antarctic and
artic, the inevitable happened. The whales who ruled the seas for
centuries became so scarce during the last century, that to-day whaling is
strictly controlled by International Whaling Commission. Thanks to efforts
of the Commission, the number of whales are now rising again. Hope the
whales will live and not share the same fate as dodos and Tasmanian
Tigers (Felis dingo. MARSUPIALIA), i.e., become extinct.
Whaling:
pre-renaissance
and postrenaissance
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Ecology for Millions
3.6. There are many examples of accelerated eco-deterioration during
19th and 20th century including decimation of specific human populations.
Those may not be relevent here. But one thing should also be admitted
that 20th century also saw rebirth of man’s interest in ecology and people
started working for nature conservancy so that before it is too late all
living beings of the world, other than human beings would have a place to
live and breed in peace.
4. REBIRTH OF ECOLOGY & ITS MULTIDISCIPLINARY NATURE
4.1. Now let us come back to Ecology. Ecology although in spirit is as old
as Egyptian culture, but is reborn in its modern garb after first World War
when all the analytical tools of applied sciences were available to aid its
pursuit. Ecology today is an applied science. It aims to unravel the
complex relationships between animals and plants and each animal
species and with each plant species and also the complex relationships
which exist between each species and their non-living environments such
as, soil water, light, heat and air etc. Hence Ecology has to draw upon
various relatively pure sciences such as, morphology, taxonomy,
behaviour, embryology, physiology, genetics, chemistry, physics,
mathematics, geology, geography and metereology etc. Thus a true
ecologist does not hestitate to draw upon any branch of knowledge which
suits his need—particularly physics and chemistry and statistics. With
time and experience ecologists are increasingly drawing from other areas
of science besides these (as above). So the tree of ecology has many roots
and many branches (Fig. I.2 ).
5. AIM OF THIS BOOK
5.1. Despite its relevance in today’s context the basic oncept of ecology
is still understood by only a few. The literature is full of technicalities and
not easy to follow. Interestingly however, the basic principles of ecology
can be presented to the general public without using technical jargon.
5.2. This small book is an humble attempt by the author to take the basic
concepts of ecology to the common man. It is common man or woman who
matter as, it is he and she alone who by their intelligent or unintelligent acts
can make or mar their environment. Much of the future happiness of
mankind is hinged upon how man uses his environment and habitat.
5.3. I have deliberately avoided technicalities lest these would limitise the
size of the target population and thus the effectiveness of the book. Also
my experience of teaching ecology in university has convinced me that
the ecological principles can be understood without technical jargon. For
interested readers however, information regarding technical literature is
given in appropriate places.
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Introduction
11
TREE
OF
ECOLOGICAL
KNOWLEDGE
THE BRANCHES
OF
KNOWLEDGE
ECOLOGY
DRAWS UPON
Ma
G
G
eo
og
ati
m
the
sics
Phy
y
l
eo
cs
Mar pho
r io
cte
Ba
Chemistr
y
Taxono
my
y
log
og
iol
Ph
ys
Be
ha
vi
y
ou
r
g
p
ra
hy
O
th
er
s
rs s
he
Ot n e t i c
y
Ge
log
yo
r
b
Em
Figure I.2 Areas of Sciences which Ecology presently draws upon.
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12
Ecology for Millions
6. A BIRD’S EYE VIEW OF THIS BOOK
6.0. Efforts are made to explain step by step the basic principles of
ecology and show our readers how these principles can be used for
judicious use of the abundant resources of Nature for benefit of all and
with detriment of none.
6.1. At the outset, a few words have been spent to trace the dawn of
ecological consciousness amongst early human societies & also
emergence of the formal word of “Ecology” amongst branches of
sciences (Chapter I, INTRODUCTION : The Beginning).
6.2. Then it has been shown how, when a piece of “Nature” if left
undisturbed, leads to a mutually-reactive but self-sustaining situation
generally known as ecosystem. Thus a forest is an ecosystem, a lake is an
ecosystem, a desert is an ecosystem and so on; (Chapter II,
ECOSYSTEM : The Garden of Eden).
6.3. In the following chapter endevour has been made to show how
bountiful Mother Nature is and how her bounty and blessings can be
managed so that there is enough for all including animals (Chapter III,
PRODUCTIVITY : Mother’s Bounty).
6.4. Here it has been shown how the energy from sun, which is the
ultimate source of energy of our planet Earth, is trapped by green plants
for synthesising biomolecules which in their turn power all the activities
of living beings. In the final analysis energy from sun is the fountainhead
of the entire human civilisation since its dawn (Chapter IV,
BIOENERGETICS : Sun the ultimate Source of Energy in Earth).
6.5. Following these chapters we have taken up the elucidation of the
methods which Nature adopts to ensure the continuity of the flow of life
on earth and how her bounty, or in other words how the cycle of birth and
death are really supportive of each other and leads to the establishment of
an eternal cycle (Chapter V, BIO-GEO CYCLES OF CHEMICALS : The
Eternal Cycle).
6.6. and 6.7. Our next two chapters will lead us gradually into the areas
which show us what regulate the increase or decrease of a population in a
place and how skilful tending of Nature is primal for survival and growth
of all living beings. These will also show us how application of this
knowledge can help us to provide for all plants, animals and human
beings (Chapter VI, POPULATIONS : The Milling Millions & Chapter VII,
COMMUNITIES : The Noah’s Arc).
6.8. After these a brief presentation has been made of the specialities and
beauties of the various parts of Earth (Chapter VIII, BIOMES : Nature in
Her Splendour).
6.9. Near the end of this small book an outline has been drawn up of the
various types of disturbances in ecosystems, most of which are caused
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Introduction
by human activities. The various causative agents of such disturbances
are broadly termed POLLUTANTS. These pollutants are gradually
throttling our ‘Garden of Eden’ (Chapter IX, POLLUTION : Tortures to
the Nature).
6.10. Finally before closing this book I have tried to put down to the best
of my understanding of and in brief, what are our duties and obligations
to Nature who nourishes all of us and how best we can discharge these
duties and obligations in the light of our newly acquired perception of
Ecology (Chapter X, PROBLEMS AND SOLUTIONS: Challenges and
Rising to Them).
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The Ecosystem
15
Chapter II
The Ecosystem
(The Garden of Eden)
Topics
II.1. Ecosystem : Early Confusions in Meaning And Emergence of
Present Definition
II.2. Main Types of Ecosystems
II.3. Human Interference And Damages to Ecosystems
II.4. Other Types of Ecosystems
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The Ecosystem
17
CHAPTER II
THE ECOSYSTEM
(The Garden of Eden)
“I went to the woods because I wished to live deliberately, to front only the essential
facts of life, and see if I could not learn what it had to teach, and not, when I came to
die, discover that I had not lived.”
— Henry David Thoreau.
1. ECOSYSTEM : EARLY CONFUSIONS IN MEANING AND
EMERGENCE OF PRESENT DEFINITION
1.1. With the birth of Ecology in late 19th century, as a distinct branch of
Natural History, research on this baby science began in earnest in both
sides of Atlantic. Soon useful information began to appear in journals.
The area however being unchartered the observations were mostly
descriptive. Methods varied from person to person and consequently their
data were not easy to compare. There were ample scope of confusion as
to exactly what a worker meant and how to compare one’s observations
with another’s somewhat similar observations elsewhere. Rarely the
parameters of two workers would mean the same. Indeed they did not.
Clear and precise meanings of parameters with comparable data were
necessary. Then only one could meaningfully compare the data of one
with another.
Early works in
Ecology and
confusions in
meanings
1.2. Gradually through various studies it became apparent that an area or
habitat (i.e. a section of our biosphere) if it has to have stability in its
nature, must have at least four distinct features. These are—
(a) Some green plants who produces food
(b) Some animals who live on green plants
(c) Some bacteria and fungi which live on dead (a) & (b)
(d) Some soil, water, air and sunlight which support the above.
Plants produce food using sunlight and other components of (d),
animals survive by sonsuming plants and after their death both animals
and plants return all the materials locked up in their bodies back to (d) via
decomposition through (c). Thus a self-sustaining environment is formed:
from (a) to (b) from both (a) and (b) through (c) back to (d) and from
(d) again back to (a). Thus the eternal cycle of life goes on and on
(Fig. II.1.).
Definition of
Ecosystem
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18
Ecology for Millions
a
Green plants
c
Animals
b
Soil, water, air & sunlight
Figure II.1 The eternal cycle of Life in Ecosystem.
Ecosystem and
Components of it
1.3. After several such descriptions of self sustaining habitats by
ecologists both in Europe and in America, the definition of Ecosystem
offered by English Botanist A.G. Tansley (1935) seemed most
appropriate. According to Tansley all the living beings of a place ( i.e.
plants, animals and bacteria etc.) along with their habitat ( i.e. physical
and chemical components of environment) when interact and produce a
recognisable stable entity, the place may be called an ecosystem (1935).
An Ecosystem contains adequate amount of Autotrophs* (green
plants—trees, grasses, algae etc. which can produce their own food),
Heterotrophs (animals-herbivores, carnivores etc.), bacteria etc. which
feed upon the matter produced by the autotrophs), Saprotrophs (bacteria,
fungi etc.) and the Abiotic Components of surrounding environment
(soil, water, air, light and heat—ingredients used by autotrophs to produce
food). The above four factors or features autotrophs, heterotrophs,
saprotrophs and abiotic components, interact with each other in such a
fashion as to create a more or less stable and self sustaining unit of
environment. Such a self-sustaining unit of Nature is an ECOSYSTEM. A
large forest, a lake, a coral reef, a mangrove forest or a desert, all , if left
undisturbed and remain self sustaining, are ecosystems. So henceforth we
shall call these components namely, autotrophs, heterotrophs saprotrophs
and abiotic components as the four basic components of all ecosystems.
2. MAIN TYPES OF ECOSYSTEM
2.1. With a little imagination we can easily see that ecosystems can be of
various types. For example, a lake or a large pond can be an ecosystem as
these are self-sustaining; so is a forest and so on. Human interference
often robs ecosystems of their self-sustenance and thus kills them. A
detailed examination of a simple ecosystem say, a large pond or a small
lake, will help to understand the basic fetures of ecosystem. (Fig. II.2.).
*TROPHISM concerns the method by which a living being procures food. A
living being which produces its own food is an Autotroph such as a green plant.
Similarly a living being which cannot produce its own food but instead, depends on
food prepared by plants is an Heterotroph such as animals, and a living being which
produce food by breaking down dead plants or animals is a Saprotroph such as fungi
etc. We human beings are heterotrophs.
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The Ecosystem
Figure II.2 Pond as an Ecosystem
19
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20
Ecology for Millions
Here it must be pointed out that often heterotrophs mean both
heterotrophs and saprotrophs.
Pond: A Simple
Ecosystem
2.2. In a pond (or lake) we shall find algae, green weeds and phytoplanktons*. All these have chlorophyll (a green plant-pigment). With the
help of chlorophyll and energy from sunlight these plants synthesise starch
from simple raw materials such as CO2 and O2. So these green plants etc.
are the first component or autotrophs of a pond or lake. Besides the
autotrophs in a pond or lake there are fishes, insect-larvae, turtles, zooplanktons* and bacteria etc. None of these have chlorophyll so these
cannot synthesise food (starch) as autotrophs can. So these must obtain
food by consuming plants (as do fishes, cows, human beings, insects, zooplanktons etc.) or by consuming dead and decomposing bodies of plants
and animals (as do bacteria and fungi etc.). Therefore fishes etc. and
bacteris etc. both of which obtain food from plants either fresh of
decaying beings form the second and the third components i.e. the
heterotrophs and saprotrophs respectively of a pond or lake. Finally the
non-living components of the environment, where the autotrophs live, i.e.
soil, air, water and sunlight etc. and which the autotrophs utilise to
synthesise food, form the third component or abiotic components of a
pond or lake (Fig. II.2).
2.3. This must also be remembered that besides providing raw materials to
autotrophs for synthesis of food, the abiotic component of an ecosystem
forms the bulk of the environment on which both auto hetero and
saprotrophs depend. From a sentimental angle one can say that abiotic
components form the umbililcal cord of an ecosystem.
2.4. These three main components i.e. autotrophs, heterotrophs and abiotic
components are musts for any self sustaining ecosystem. Unfortunately in
many instance men in power either through ignorance or being blinded
with short-term gains, neglect one or more of these vital components and
still want to create a ‘garden’ or ‘reserve forest’ or a ‘national park’.
Naturally they fail and not knowing the cause blame each other.
Some well known
ecosystems
2.5. Here it would be worth while to emphasise once again that presence
of autotrophs, heterotrophs and abiotic components all in ample i.e.
balanced quantities are musts if an ecosystem is to be self-sustaining or
more or less permanent. Large ponds, lakes, large forests, large rivers,
large gulfs or seas are generally self-sustaining. So these are named as
lake-ecosystems, forest-ecosystems and gulf-ecosystems etc. Examples of
the above are Chilka Lake Ecosystem, Sundarbans Ecosystem of India
and Gulf of Mexico Ecosystem of Mexico respectively. Lake Victoria of
*PLANKTON are small mobile or passively flowing organisms in natural bodies
of waters such as pond or lake or sea. Those who have chlorophyll and hence can
manufacture food are called phytoplanktons and those who do not have chlorophyll
and hence depend for food on phytoplanktons are called zooplanktons.
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21
Africa, Mudumalai Forests, Corbet National Park of India, Amazon River
Valley of Brazil, Lake Baikal of Siberia, Rain Forests of Amazon valley
of Brazil and Great Barrier Reef of Australia are some of more
spectacular ecosystems of the world offering challenges and rewards to
any ecologist who works there. There are many more very interesting
ecosystems found in different regions of the world. In the accomanying
map the locations of some of the large and relatively undisturbed
ecosystems of the world have been pointed out (Map II.1.).
2.6. Here it would be worth emphasising once again that the presence of
autotrophs, heterotrophs and abiotic components all in ample quantities are
musts for all self-sustaiing ecosystems. If any one of these three vital
components are disturbed beyond the limit of tolerence (specific for each),
the other two components are affected as well, mostly adversely. For
instance until too many trees are cut down large forests are self-sustaiing.
Similarly until too much pollutants poured in or dams are built or too
much water is taken out for irrigation, large rivers are self-sustaining and
so are large gulfs or small seas untill too muching fishing or too much
dredging is carried out. Unfortunately to-day with many ecosystems such
ills are happening.
3
1
2
Tundra
Boreal Forest
4
Temperate
5
Forest
Desert
6
Savannah
Tropical
Rain Forest
7
8
Temperate
Grassland
Mountains
On self-sustainance
of eco-systems
9
10
Map II.1 Some well-known Ecosystems of the world
Temperate
Rain Forest
Scrubland
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22
Role of Watershed
and importance
monsoon recharge
Rainwater and
Water Management
Ecology for Millions
2.7. For long-term survival a lake or even a pond or a small impoundment
of water, must be quite deep and have a large water-shed*—about 50
to 100 times of their actual areas. Rain-water from the surrounding land
i.e. the watershed accumulates into the lake or pond and also percolates
into the deeper layers of the soil of the watershed. If during monsoon
enough rainwater is allowed to enter the watershed then, during the dry
season this ground water accumulated during monsoon, gets gradually
released into the lake or pond and keep then alive till next monsoon. If on
the otherhand, the land surrounding a lake or pond etc. become covered
with buildings, roads and pavements etc., then the rain water instead of
entering the soil gets quickly washed into the drainage system and thence
into the rivers. In such a situation the ground-water does not get a chance
to get replenished during the monsoon. Consequently such impoundments
of water (lakes, ponds all) gradually dry up and the dependant ecosystem
lost.
2.8. That is exactly what is happening with the small ponds of Kolkata
and the wetlands in the suberbs of Kolkata. Only the ponds of ‘Maidan’
area and ‘Dhakuria Lake’ are surviving. This is because their watersheds
are still largely uncovered with buildings and roads etc. Summarily
sustainability of any ecosystem depends upon a balance of all the main
components of the ecosystem concerned i.e., a balance between the
autotrophs, heterotrophs and abiotic components. Water is a vital abiotic
component of any ecosystem. Small shallow ponds tend to dry up in
summer when, their animals etc. i.e., fauna** either migrate away or die
off. Hence most shallow ponds behave like temporary ecosystems. Large
deep ponds or lakes however are more stable. Some examples of such
stable ecosystems are Lake Victoria of Uganda, Great Lakes of U.S.A.
and Lake Baikal in Siberia.
3. HUMAN INTERFERENCE AND DAMAGE TO ECOSYSTEMS
3.1. No lake however big is insulated from its surrounding basin or
watershed. Aral Sea of erstwhile U.S.S.R. was a big land-locked lake (150
miles × 100 miles), fed by two rivers Syr Darya and Amu Darya, and
hence was apparently permanent. But the Russians have taken out so much
water from these two rivers for mega-irrigation schemes that today this
huge lake has shrunk to nearly half of its original size. This has happened
within a short span of 30 years (National Geographic Society).
3.2. Just as the lakes are susceptible to the abuse of their watersheds so
are the rivers. The Ganga river ecosystem of India has suffered similar
*WATERSHED is the region or the area from where water is drained into a pond,
a lake, a swamp or a river.
**Fauna & Flora : are the collective names of animals and plants of any place
respectively.
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The Ecosystem
23
damage owing to extensive irrigation canals and other causes such as, silt
deposits and pollution. In a river ecosystem water supply depends mainly
upon three factors—
(i) adequate snow and glacier in its area of origin ( when a river
originates from snow capped mountains as
Ganga does),
(ii) the regularity of rains upon its watershed and
(iii) the nature of vegetation which covers the watershed.
If any of these three factors are destabilised the river flow is affected. Let
us examine these one by one using river Ganga of India as an example
(Map II. 2.)
(i) Snow and Glacier. The Northern tributaries of Ganga such as
Yamuna, Ganga and Gharghara and others all origin in the
glaciers of Himalayan ranges. Therefore adequate snowfall in the
upper mountain ranges and glaciers of Himalayas is necessary
for healthy beginnings of Ganga and her tributaries. Hence
unless plenty of snowfall takes place in Himalayas Ganga’s owe
may begin right at her origin. Nowadays owing to rise of CO2
content and other gases of atmosphere there is a gradual rise of
the atmospheric temperature of the world. This phenomenon is
called ‘global warming’ (for explanation pl. see ‘Carbon Dioxide
and Greenhouse Effect’ in chap V). Owing to this rise in CO2
76
32
88
80
84
E
28
24
Map II.2 The watershed of river Ganga
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Ecology for Millions
content of atmosphere and consequent rise in atmospheric
temperature the annual snowfall also gets reduced. This has a
serious negative effect on the water supply of snowfed rivers
such as Ganga and her tributaries. However for reasons not yet
adequately understood, one year’s low snow fall is ususally
followed by high snow fall in the following year. Hence factor
(i) is not yet identified as problematic.
(ii) Rains on the watershed. Here we have more information. The
average annual rainfall of India, excluding Rajasthan, but
including Himalayan region and Eastern India, fluctuates around
100′′ . Rainfall in Rajasthan varies from 5′′ or so in district of
Jaisalmer to 25′′ or so in district of Kota; in Himalayan ranges
the rainfall is around 150′′ while in Eastern India particularly in
and around Cherrapunji Hills the rainfall is highest in the world—
around 500 ′′ .* This huge annual rainfall on the Himalayan
ranges directly affects their watersheds and thus the rivers which
origin thence. River Ganga and her Northern tributaries (Map
II.2.) are direct beneficiaries of this rainfall.
The Sponge Theory
(iii) Nature of Vegetation and sponge effect. Vegetable cover of the
mountain ranges and hills and the rest of the watershed is
extremely important for recharging the groundwater and thus the
health of any ecosystem including river ecosystem, (such as
Ganga). This is how this happens. Rainwater before reaching a
river must roll down the surrounding slopes. In an undisturbed
river ecosystem both the hills and the valley are normally covered
with trees and ground vegetation. The roots of these keep the
soil bound and the leaf canopy of trees and vegetation stop the
rainwater from directly hitting the ground. Hence a good portion
of rainwater gets opportunity for gradual penetration into the soil
and the remaining water overflows into the rivers with only very
low soil content as, most of the ground is bound with roots and
covered with vegetation (Table II.1). This gradual absorption of
rainwater by soil is comparable with sponges’ absorption of
water hence this concept is known as ‘Sponge Theory’. This
penetration of rainwater into the soil helps in the survival of an
ecosystem in at least six ways:
(a) Recharges the aquifers i.e., the water-bearing strata of the
ground.
(b) As a result of (a) the arsenic content of well-waters remains
low.
*Alas even Cherrapunji could not escape the dark hand of human interference.
To-day Cherrapunji suffers from draught in summer.
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The Ecosystem
25
(c) Trees suffer less from summer draught.
(d) Keeps the silt load of river waters particularly in the
monsoon, low.
(e) Consequent upon (d) the damages caused by floods are
kept relatively low, and
(f) Keeps the ecosystem healthy by encouraging balanced
survival of flora and fauna pertaining to the watershed.
The above points (i) to (iii) and (a) to (f) and the earlier principles
delineated so far are the ecological bases of an healthy and balanced
ecosystem. Violation of any one of the above causes havoc in the
ecosystem and this we may not realise in the beginning and when we do,
often only when too late. It is however very much possible for human
beings to survive in any ecosystem if we only take prior notice of the
nature of the ecosystem and determine how much it can be milched
without detriment to its long-term health.
Table II.1.
EFFECT OF GRASS-COVER ON RUN OFF AND SOIL LOSS
(From State of India’s Environment: A Citizen’s Report–3, 1991. By Centre for
Science and Environment, New Delhi)
S. No.
1.
2.
3.
4.
Situation
Bare fallow
Bare and ploughed fallow
Natural grass
Grass cover
Runoff as % of Rainfall
Soil Loss (t/ha/yr)
71.1
59.6
21.2
27.1
42.4
155.9
1.0
2.1
Here we shall present two examples to show how as a result of
ignorance neglect of the above concepts the Ganga ecosystem of India
has become much deteriorated.
(A) Lions and tigers of India. During the reign of emperor Asoka,
lions were common all over India. The beautiful lion-heads of Asokan
pillars—which form the seal of Govt. of India, were not figments of
imagination of sculptors. As a matter of fact lions proudly strutted along
throughout western Asia from Mediterranean to South Africa. Today the
Indian share of these regal animals, are only a few left as ‘protected
animals’ within the confines of Gir Forest of Gujarat. Now about the
tigers. As late as beginning of this century (1900) tigers were abundant in
Central India, Terai forests of Himalayas, Eastern India and Sunderbans of
Bengal. Their number was around 50,000 or so. Today their number is so
dangerously low that these royal animals had to be declared protected and
their hunting prohibited. Credit goes to Late Prime Minister of India Mrs.
Indira Gandhi for doing so. Still today they are found only in small
pockets—reserve forests of India. This shocking decline of tiger
population of India is quite clear from the following table (Fig. II.3). Here
is what Zuber writes on this tragedy in his book (p. 47). “There have
Some major
damages to Indian
Ecosystem
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26
Ecology for Millions
40,000
40,000
(1920)
30,000
30,000
(1940)
20,000
15,000
(1960)
10,000
1820
(1972)
No.
Yrs
1920
1940
1960
1980
Figure II.3 Decline of Tiger population of India during this century
been Maharajas who have boasted of holding the world’s record for the
numbers of tigers they killed. Three of them have killed 1000 tigers
spiece (1978).
They are like Indian counterparts of Buffalo Bill* of U.S.A. We feel sure
there would be similar record holders’ amongst the elephant and lion
hunters of Africa. These are glowing examples of ignorance and vanity.
Increased soil-loss
owing to ploughing
& tree-felling
(B) Soil loss through river-waters. Soil loss during rains from
grass-covered soil is considerably less than from bare soil (Table II.1.).
Also, more water rushes into rivers from bare soil than from grasscovered one (table as above). The enormity of this loss of soil will strike
us like a hammer if only we look at the following figure (Fig. II.4.).
‘The river Ganga, Brahmaputra and Indus’ together account for over half
of the total silt load of Indian rivers’ (Indus now mostly flows through
Pakistan); but not even a fifth of their silt-load come from Himalayan
mountains. The ‘black soil’ region of Central India alone generates an
estimates 3,376 mil. ton of eroded soil—averaging a rate of 50 ton/
hectare year (State of India; Environment : a Citizen’s Report - 3, p. 54).
Details given in the above table and figure. This huge rush of soil during
monsoons from river-valleys into the rivers—here Ganga and her
*Buffalo Bill—A folk hero of 19th century in U.S.A. who seems to have killed
alone maximum number of bisons, partly as sport and partly to provide meat for men
laying railway lines to open up the frontiers.
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The Ecosystem
27
→ 29% deposited in seas
10% deposited
→ in dams
→ 61% deposited in rivers
Figure II.4 India’s annual soil erosion: About 5,400 million tons of soil of India is eroded every year—
mostly during monsoons. Ganga and Brahmaputra alone contributed one-fourth of total ocean deposits.
branches, fill up their beds with silts as a result of which floods are
becoming more frequent and more devastating every year. The following
table (Table II.2.) and figures (Fig. II.4.) respectively show, how the area
affected with floods and the consequent damages, on an all-India basis,
have increased dramatically over the years.
Table II.2.
AREAS OF INDIA AFFECTED BY FLOODS IN SUCCESSIVE DECADES
(From State of India’s Environment: A Citizen’s Report–3, 1991. By Centre for
Science and Environment, New Delhi)
Decades
1950
1960
1970
1980
Area Affected (in million ha)
6.86
5.86
11.19
16.57
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Lowering of ground
water level
Arsenic poisoning
of well water and
how that happens
Ecology for Millions
(C) Inadequate Recharging of Aquifers. Another consequence of
mismanagement of an ecosystem is arsenic poisoning. Unfortunately
planners usually don’t seem to understand this. Here is how it happens.
Owing to the lack of tree/grass cover and poor management of monsoon
rains, the rain-water runs off into Ganga too quickly, before adequate
water can penetrate into the deeper layers of the soil and recharge the
water-bearing strata of the soil i.e. the aquifers. Normally the recharging
of aquifers also wash down the poisonous salts of soil such as arsenic
into still lower levels from which water is isually not tapped. (This process
of ground water sinking down to lower levels carrying along with it
various salts in solution is generally known as leaching). However when
there is good plant-cover, rain water gets enough time to penetrate into
soil (through sponge action) before the surplus water is washed into the
rivers (Tab. II.1). So leaching takes place. But in bare soil this does not
happen. on the otherhand due to quick run-off of water from the ground
surface, these natural processes of recharging the aquifers and leaching
are thawarted. From the above two things happen.
One, the ground water level level goes more and more down and
two, the arsenic salts which are common in soils get slowly released
into soil-water (and instead of being washed down by monsoon waters),
rise above and mixes into the well-waters. This is the cause of recent
frequent findings of arsenic in many well-waters which did not have
arsenic earlier.
Wrong way of
paving foot-paths
Paving of foot-path prevents penetration of rain-water into soil.
In Kolkata most footpaths are already paved and in its suburban Salt Lake
City the same is being done. Footpaths when paved should leave adequate
entry points of rainwater into the soil and not let all water run off into the
river Ganga. This simple precaution is not taken. The inevitables are
happenning. The level of ground water is going further and further down
every year, tubewells have to be sunk deeper and deeper for water, ponds
are drying up, endemic fishes are vanishing and more and more trees are
scccumbing to draught every summer. These are some common
tragedies which can be easily prevented if the planners take into account
the elementary principles of ground-water management and how to
maintain the health of an ecosystem by linking proper ground water
management, with town planning.
In the Ganga river watershed all the above tragedies are happening.
We repeat, briefly these are
* Frequent landslides in the Himalayas owing to unbriddled
deforestation;
* Frequent floods in the rainy season owing to silting of river beds
from silt-loaded waters and;
* Frequent severe summer draughts owing to progressive lowering
of ground water levels and
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29
* Arsenic poisoning in well-waters due to reduced leaching
(explained above).
In Rajasthan which is a semi-arid state of India, rainfall ranges from
only 10-25′′ inches annually, so the wells are very deep averaging 125 to
175´ feet each. Here owing to insufficient leaching many well-waters are
poisoned with various salts particularly arsenic. Well-water is generally the
only source of water for villagers in drier districts like, Jhun Jhunu,
Barmer and Jaisalmer. A significant percentage of villagers who use wellwater for drinking suffer from arsenic poisoning. But there is another
source of drinking water available only to some residents of such dry
places. Rich people who live in brick houses with paved courtyards store
all the rainwaters washed down from roofs and courtyards into large
underground reservoirs. Such rich people drink throughout the year only
this stored rain-water and not the well-water. None of such people suffer
from arsenic poisoning.
Drinking water in
Rajasthan villages
3.3. Summing up, this may be safely said that the present state of Ganga
River watershed is an excellent example of how an ecosystem should not
be handled and this also shows that use of the basic concepts of ecology
in planning and management of forestry, agriculture and town planning,
can vastly improve the health of an ecosystem or watershed adding to
economic gains as well pleasure to all inhabitants man, plants and animals.
4. OTHER TYPES OF ECOSYSTEMS
4.1. In the previous paragraphs we have outlined what are the basic
features of an ecosystem (which are autotrophs, heterotrophs,
saprotrophs and abiotic environment), using pond as an example, and
following that were what calamities may result when an ecosystem is
mismanaged using Ganga river watershed as an example. Besides pond (or
lake) and river there are other ecosystems in our biosphere*. These are
forests, seas, gulfs, coral reefs, mountains, islands and deserts. Each has
its own specialities as well as susceptibilities to human abuse. At this stage
we shall not delve into these details but rather talk more about these in a
later chapter VIII - THE BIOMES (The Nature in Her Splendour).
4.2. Besides these natural ecosystems, there can be other types of
ecosystems which are mostly small and of temporary nature such as, an
aquarium for small fishes, an aviary housing small birds, a vivarium for
small land animals or a dead tree lying on a forest floor with its host of
boring insects and fungi or a bag of stored grain with insect pests. All
these are like ecosystems in small scale. These are Microecosystems. A
*Biosphere—The this upper part of the earth's crust containing water and air,
which contains all the living beings of earth. So all ecosystems are components of
biosphere only.
Micro-ecosystem
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Ecology for Millions
microecosystem is like an ecosystem but not quite. An ecosystem is self
sustaining but a microecosystem may not be so . From time to time
many microecosystems may need inputs of one form or other for their
continuance. Besides these are very small hence—micro. However within
the confines of its limited space a microecosystem exhibits all the
characteristic features (save self-sustainance) of an ecosystem. For
instance an aquarium. A glass aquarium 1 metre wide, 1 metre deep and
2 metres long which besides water has 3-5 cm. thick floor of earth and
gravel, some algae (autotrophs), a few small vegetarian fishes i.e.,
heterotrophs and presumably some saprotrophs, may easily form a
microecosystem (Fig. II.5).
Figure II.5 A Microecosystem (glass aquarium)
4.3. If this aquarium with all the above components is placed near a
window or a verandah where it can get some sunlight, this will behave
like a microecosystem. With careful choice of fish and its number and
proper management this aquarium may even be self-sustaining unit of
biosphere i.e., an ecosystem but on a very small scale - in microscale.
Similarly a small lawn of grass (autotrophs) with a few grasshoppers
(heterothophs), soil, some small soil inhabitants (saprotrophs), water, air
and sunlight as abiotic components may act as a microecosystem.
Microecosystems are very useful for experimental studies of various
aspects of ecosystems within a laboratory or field. These are also
excellent tools for teaching children ecology at home.
These microecosystems however mostly require supervision or
monitoring so that none of the essential components become too much or
too little.
4.4. In contrast with microecosystems large ecosystems such as forests,
rivers etc. are called macroecosystems. All macroecosystems however
house various microecosystems. Different areas of the same forest may
vary qualitatively from location to location leading to pockets characterised
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The Ecosystem
by their own microecosystems. For instance, the canopy of a large
tropical rain forest and the undergrowth of the same forest will differ
widely in their nature of the autotrophs, heterotrophs and in the amount
of sunlight available to them. Hence it is always desirable for an ecologist
to define precisely the nature, location, size and position etc. of the
ecosystem he is referring to. Or in other words the ecologist is expected
to define precisely the parameters of the ecosystem he is working with.
Otherwise it may not be possible for another worker to repeat the
experiment of the ecologist and check his observations. This repeatability
is very important for ensuring the reliability of any observation and
experiment.
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Chapter III
Productivity
(Nature’s Bounty)
Topics
III.1. Meaning of Productivity
III.2. Types of Productivities
III.3. Measurement of Productivity
III.4. Factors Limiting Productivity
III.5. Some Interesting Examples of Productivities
III.6. Some Important Physical Factors’ Role in Influencing Productivity
III.7. Ecological Niche—The Hutchinson Concept
III.8. Eras of Human Civilisation : Rise in Productivity and Population
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CHAPTER III
PRODUCTIVITY
(Nature’s Bounty)
1. MEANING OF PRODUCTIVITY
1.1. Productivity is the rate at which biomaterials are being produced, by
all the autotrophs (i.e. green plants) together and inhabiting a defined unit
of biosphere (i.e. an ecosystem), within an unit of time.* Usually the
amount is measured in kilo-calories and time in days, months or years.
Again this 'defined unit of biosphere' depends upon the worker and his
needs. The more biomaterial is produced in an unit of time the more
productive the ecosystem is. For instance a forest is more productive than
a desert. Here are the productivities of a few well-known ecosystems
(Table III.1.)
Definition
Table III.1.
PRIMARY PRODUCTIVITIES OF SOME MAJOR ECOSYSTEMS
(Adapted from a Table of Ecology of Eyewitness Science)
S.No.
1.
2.
3.
4.
5.
6.
7.
8.
Ecosystems
Productivities (Kcal/Sq. M/Yr)
Extreme Deserts
Scrub Deserts
Open Ocean
Continental Shelf of Oceans
Lakes
Industrial Agriculture
Tropical Swamps and Marshes
Tropical Rain Forests
60
1200
2400
6500
9000
12500
35000
36000
2. TYPES OF PRODUCTIVITIES
2.1. A portion of the biomaterials produced by the autotrophs is used up
by the autotrophs themselves for their sustenance. (By sustenance we
mean all metabolic activities such as growth, reproduction and locomotion
etc.). The surplus biomaterial only is available to the heterotrophs (i.e,
*Productivity is a general term which means rate of production of any item,
material or otherwise ( such as intellectual ). In this book however we shall concern
ourselves only with the production of biomaterials.
Gross and Net
Productivities
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Ecology for Millions
plant eaters) of that ecosystem. The first quantity i.e. the entire
biomaterial produced by the autotrophs of that ecosystem, i.e. including
their own consumption, is known as Gross Productivity and the amount
which remains for use of the heterotrophs is known as Net Productivity.
Primary, Secondary
and Tertiary
Productivities etc.
2.2. Just as autotrophs synthesise biomaterials, by using simple inorganic
materials with the help of sunlight, the heterotrophs (i.e. herbivores,
carnivores etc.) too, in their turn, produce biomaterials by consuming
plant products or other animals respectively. To distinguish the production
of autotrophs from those of heterotrophs, the productivity of green plants
is termed Primary Productivity, of herbivores Secondary Productivity
and of carnivores as Tertiary Productivity. By extending this logic
further, the productivity of lice etc. which live by sucking the blood of
carnivores such as, lions or tigers etc., can be termed Quaternary
Productivity.
2.3. Now let us summarise all the types of productivities explained
above as follows:
(1) Gross Primary Productivity (GPP)—the total amount of
biomaterials synthesised by autotrophs.
(2) Net Primary Productivity ( NPP)—that portion of GPP that
remains to be available to the heterotrophs.
(3) Gross Secondary Productivity (GSP)—the total amount of
biomaterial synthesised by herbivores.
(4) Net Secondary Productivity (NSP)—that fraction of the GSP that
remains to be available to the carnivores.
Similarly (5) GTP and (6) NTP denote Gross and Net Tertiary productivities respectively and so are the meanings of (7) GQP and (8) NQP.
2.4. One more point. All productivities are measured as the amount of
biomaterial produced within a fixed period of time. Hence both the amount
of biomaterial produced and also the time period within which this amount
is produced are the two essential parameters for measuring any type of
productivity. Here are one example each of four types of producers.
(a)
(b)
(c)
(d)
Grass
Deer
Lions
Fleas
—
—
—
—
Primary producer
Secondary producer
Tertiary producer
Quaternary producer
All these four types of producers are found in any large ecosystem.
Corbett National Park of India and Serengeti National Park of Afrika are
two of many such ecosystems.
3. MEASUREMENT OF PRODUCTIVITY
3.1. We now have a broad idea about what productivity means to an
ecologist. The next question that comes to our mind is how to measure
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37
productivity. Here we shall present two simple methods of measuring
productivity in two different situations.
3.2. As early as 1927, T. Gaarder and H. H. Gran devised a very clever
experiment for measuring - both gross and net productivities, of an aquatic
ecosystem. First the principle. During photosysthesis the plants produce
biomaterials with the help of their green pigment i.e., chlorophyll, using
carbon dioxide and water with energy from sunlight. During this process
oxygen is released. So simply, photosynthesis can be shown as follows :
CO2 + H2O + energy (from sunlight) and help of chlorophyll
CH2O + O2
CH 2 O is a very simple biomolecule from which other complex
biomolecules are made. So the net direct outcome of photosynthesis is the
production of CH2O and O2 (oxygen) and removal of CO2. Therefore if
we can measure how much CO2 is taken up or, how much O2 is released
from the ecosystem we shall know how much biomaterial is produced.
Here we must not forget that oxygen is also used by plants themselves in
their own respiration. Therefore whatever oxygen that comes out of the
ecosystem is that which is surplus after providing for respiration. This
information is what Gaarder and Gran used. They measured the amount
of oxygen released during a fixed period of time by a fixed amount of
photosynthetic plants and also determined the amount of oxygen that was
used up during the same period by the same plants. By adding one with
the other they got the total amount of oxygen produced during
photosynthesis by the same plants. From this sum total of oxygen
produced, Gaarder and Gran determined the amount of biomaterial that
was synthesised by these plants during that period. Following is the
technique.
3.3. Three empty bottles of equal size were filled up with water from the
same depth and preferably near the surface of a pond/ lake which is welllighted and has normal phytoplankton flora, i.e., the water not crystal clear
but rather somewhat greenish. The bottles are marked ‘A’, ‘B’ and ‘C’.
The O2 present in the bottle ‘A’ is immediately fixed with chemicals so
that, both photosynthesis and respiration are stopped in this bottle. The
bottle ‘B’ is thoroughly wrapped up in 3 layers of aluminium foil so that
no light can penetrate into the bottle. This will stop photosynthesis but not
respiration. The bottle ‘C’ is left as such i.e., unwrapped; so, here both
photosynthesis and respiration will go on as usual.
3.4. Now all the three bottles i.e. ‘A’, ‘B’ and ‘C’ are stoppered and tied
with three strings are left hanging in the same depth but near the surface
of water, so that these can receive enough sunlight, and then left there for
24 hours i.e. one full day and one full night (Fig. III.1.). After 24 hours
the bottles are lifted and their respective oxygen contents are fixed and
measured. These amounts are marked ‘a’, ‘b’ and ‘c’ respectively. As per
our assumption, ‘b’ should be less than ‘a’ as—
The Light and Dark
bottle method of
Gaarder and Gran
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Rod to hang the bottles with pond water
A
B
C
Pond water in a large container
Figure III.1 Light and Dark Bottles suspended at same depth of water.
a–b =
c–b =
O2 consumed due to respiration during this period and net
O2 produced due to photosynthesis during this period, is
obtained by deducing from the above.
Hence Net production + Consumption = Gross production
i.e. c – b = net production
and (c – b) + (a – b) = gross production.
... (1)
... (2)
So through this clever but simple experiment we can measure both
the net photosynthetic production as well as gross photosynthetic
production of a simple aquatic ecosystem. As the penetration of sunlight
diminishes along with depth, production as well as consumption of O2
depends upon the depth of water where the bottles are suspended
(Table. III.2.).
Table III.2
CHANGES IN QUANTITIES OF OXYGEN IN DIFFERENT
BOTTLES SUSPENDED AT DIFFERENT DEPTHS
(From Odum–Fundamentals of Ecology–3rd Edition, 1971)
S.No.
1.
2.
3.
4.
Depth
Top cu.m
Second cu.m
Third cu.m
Bottom cu.m.
Oxygen Change (gms/cu.m)
Light Bottle Dark Bottle
+3
+2
0
–3
–1
–1
–1
–3
Gross Production
(gms/O2/cu.m)
Community Respiration
(gms/O2/cu.m)
4
3
1
0
1
1
1
3
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3.5. The same principle as outlined above can be employed to measure
the productivities of any other type of ecosystem including
microecosystems. We however shall have to make modifications in the
techniques and, or indicators to suit the nature of the ecosystem and the
aim of the ecologist. Also the techniques for autotrophs and the
techniques for heterotrophs would not be same. Here comes into play the
wisdom and skill of the worker. Anybody who has read the works of
Louis Pasteur will understand this. Pasteur’s experiments are wonderfully
simple but precise and meaningful. In fact they are classic examples of
well-desigined experiments.
3.6. Now let us discuss another method of measuring productivity. This is
Quadrat Method. This method is used to measure productivity of a
forest or grassland or agricultural ecosystem. A fixed area such as 1
metre2 or 2 metres2 or more, as per the nature of the ecosystem and need
of the worker, is fully fenced up so that no vegetable matter produced by
the plants within this area is removed by wind or any other agency. The
amount of vegetable matter produced (dry weight) by that area in a fixed
period of time, is the Net Primary Productivity of that area during that
period. (Fig. III.2).
a
b
c
No plants
Plants
(period 1)
Plants
(period 2)
The Quadrat Method
Figure III.2 The Quadrats for Quadrat Method.
3.7. It is rather difficult to know the Gross Primary Productivity through
quadrat method as, a part of the bio-matter that is produced during this
period is used up in maintaining the metabolic processes of plants
themselves. So what we measure here is the net primary production. This
net primary production is also called as Standing Crop. However by
modifying the techniques employed and selecting parameters suitably it is
possible to estimate both gross and net production of all types of
producers—autotrophs as well as heterotrophs. For more on this topic
one can see Southwood (Southwood, T.R.E., 1978, Ecological Methods,
Chapman and Hall, London).
3.8. Usually most of the plant materials consumed by animals
(heterotrophs) is used up in their metabolic as well as locomotive
activities. Only a fraction goes in building up their bodies. As a thumbrule it is usually taken that not more than 5 to 10% of the plants
consumed is converted into the body material of the consumers i.e.,
heterotrophs. So, if we arrange plants, herbivores and carnivores one
above the other in the same order we shall get the following picture of
Biological Pyramid or
Ecological Pyramid
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Ecology for Millions
their quantities (Fig. III.3). This type of figure showing the successive
trophic levels one above the other, and also indicating their respective
amounts, like a pyramid is called Biological Pyramid or Ecological
Pyramid. In such a pyramid order of production of food (i.e.,
biomaterials) are arranged with the top carnivores such as tigers occuping
the top and the vegetation occuping the bottom position. We shall talk
more about various ways of representing biological pyramids and their
shapes in our next chapter (Chap. IV).
Carnivores
HETEROTROPHS
Herbivores
Plants
AUTOTROPHS
Figure III.3 The Biological Pyramid or Ecological Pyramid.
Web of Life (or Food
Web) and Food-chain
H
E
T
E
R
O
T
R
O
P
H
S
A
U
T
O
T
R
O
P
H
S
3.9. Animals and plants are connected to each other through the food they
eat. Here is a simple example. Deers feed on grasses and leaves of small
plants and brushes etc. The tigers feed on deers and other herbivorous
animals. Besides deers there are many other animals such, as insects,
rabbits, cows etc. who feed on grasses and other vegetables. Similarly
besides tigers there are many other animals such as owls, eagles, wolves
etc. who feed on various hervivores including deers. When these
relationships are shown graphically through a diagram we get a networklike figure which we call as Web of Life or Food Web (Fig. III.4). This
IV
Omnivores
III
Carnivores
II
Herbivores
Man
Peacocks
Sharks
Rats
Tigers
Wild
dogs
Rabbits
Snakes
Deers
Insects
Owls
Birds
Fishes
I
Green plants
Small
plants
Grass &
roots
Algae
Tree &
fruits
Figure III.4 Web of Life or Food Chain and the different levels of producers (a simplified example).
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web of life or food web shows all the links in the feeding relationships in
a community. This web is commonly worked out through the analysis of
diets.
3.10. This simple diagram of an Web of Life illustrates may important
features one of which is Food-Chain. Every animal, be it a deer or a
rabbit or a man is bound with its environment through the food it takes.
Also, ultimately all of them depend—directly or indirectly on green plants
i.e. autotrophs for survival. This link of every animal through its foods to
the ultimate producer of food in Nature i.e., green plants is called FoodChain. If we ponder a little bit on this point we shall see how every man
and woman on this earth is ultimately dependant on plants for his or her
survival. So protection to plants is verily protection to our lives. We
shall talk more regarding web of life and food-chain later.
4. FACTORS LIMITING PRODUCTIVITY (OF A POPULATION)
4.1. A potted plant if not watered regularly, first wilts then dries up and
finally dies; grass if left covered for many days by something which light
cannot pass through, will soon become yellow and finally die. What do
we learn from these observations? WATER is a must for the survival of
all plants. So also LIGHT is a must for survival of grass and all such
green plants. So water and light are two very important factors on which
survival and growth of plants depend. With more experiments and
observations it was gradually found out that besides water and light there
are other factors such as heat, some gases and some chemicals which
are also vitally important for the life of green plants. All these factors are
collectively called Limiting Factors for a population. Here is a brief
account of Limiting Factors and their roles.
4.2. As early as 1840 a German biochemist Justus von Liebig stated that
the growth of a plant in any habitat is controlled by that essential raw
material which is present in minimum quantity in that habitat. For instance,
in a pond the growth of phytoplankton may depend upon the quantity of
nitrogen salt present in water. This dependance on nitrogen will occur only
if all other elements required for growth are available in plenty save
nitrogen. Hence here nitrogen will act as the ‘limiting factor’ for growth of
pond-phytoplankton. This means that factor whose paucity limitises further
growth of phytoplanktons is the limiting factor in this habitat. If on the
other hand, nitrogen is adequate but phosphorus (which is also essential) is
not then, phosphorous is the limiting factor. Justus von Liebig summarised
such observations by stating something as follows: To survive and prosper
in a particular habitat an organism must have all the essential factors
required for its growth and reproduction in ample quantities. Any element or
factor which is not ample will soon approach the critical minimum for
further growth. So Leibig’s Law of Minimum states that no organism—
plant or animal is stronger than the weakest link in its chain of requirements
of nutrients (such as nitrogen, phosphorous etc.).
Importance of
water, Light & other
ingredients far
sustenance of Life
The Law of Minimum
by Justus Liebig
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Ecology for Millions
4.3. Like many ecological concepts this Law of Minimum is a powerful
concept with scope of application in areas far beyond mere chemical
elements. Sometimes availability of space may be limiting as for humans
and many other species today (for instance tigers). Sometimes supply of
breeding opportunities may be critical as for some mammals of today.
Here is an example from fish culture. This is not about breeding though.
Often fishermen in order to increase productivity of fish, simply add
cowdung in fish pond. Usually in many ponds nitrogen is a limiting factor
for growth of phytoplanktons. When cowdung is added, phytoplankton
growth spurts. Fishes live on phytoplanktons. So application of cowdung
which is rich in nitrogen, leads to increase in the productivity of fishes by
increasing phytoplanktons in pond. We shall touch upon these aspects
once again later when, we talk about ‘populations’ of species.
The Law of Maximum
by Victor E. Shelford
4.4. Now we shall discuss another law which also guides productivity.
Just as too little of something may be the weakest link or limiting for
growth of an organism so also too much of something may be limiting.
For example, too much heat may be limiting or too much cold, or too
much dryness or too much salt in water, all these factors in their own
habitats and for the species involved may be limiting. Victor E. Shelford
in 1913 summarised these observations in another simple law Law of
Maximum. Shelford further linked the concept of minimum of Liebig
with the concept of maximum of his and presented a combined law—Law
of Tolerence. This Law of Tolerence may be simply stated as not only
too little of something may be limiting but also too much of something
else may too be limiting for survival, growth and breeding of a population.
4.5. With a little bit of thinking we shall easily visualise that :
(1) An organism which can tolerate an wide range of variation in its
requirements will inhabit in a large area or have a wide
geographical distribution. For example - Crow.
Law of Tolerence
and Subsidiary
Concept
The Prefixes steno
and eury
(2) Conversely an organism whose capacity to tolerate variation in
one or more of its vital requirements is very little, will be able to
stay only in a small area or, have a narrow geographical
distribution. For example—Trout, a fish found in cool waters of
hill stream. These two important subsidiary concepts and the
logical follow-up of these help us to understand the geographical
distribution of many plants and animals all over the world. Hence
these are important to understand biogeography.
4.6. The prefix ‘steno’ and ‘eury’ mean narrow range and wide range of
toleration respectively, for any environmental quality. For example if, any
organism can tolerate a wide variation in temperature, its temperature
toleration will be called as eurythermal and if narrow it will be called as
stenothermal (Fig. III.5).
This figure graphically represents the previous statement. One more
point. Narrow ranges of toleration i.e., steno can either be in the low end
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High
Range of toleration
2 Steno-
3 Steno-
Low
1 Eury-
Low
Environmental factors.
(Temperature or humidity or salinity etc.)
High
Figure III.5 Types of Ranges of Toleration of various organisms to a
particular environmental factor such as temperature or humidity etc.
of the range or high end of the range. When at the low end it is called
oligo and when at the high and it is called poly. Further to specify the
factor concerned a suffix is used such as—
for Temperature one may use Eurythermal or Stenothermal,
” Water salinity ”
”
” Euryhaline or Stenohaline and
” Food habit
”
”
” Euryphagus or Stenophagus.
So workers are advised to use their own judgements and observations
to decide about the prefixes to the factors whose effect on the species they
may be studying.
5. SOME INTERESTING EXAMPLES OF PRODUCTIVITIES
5.1. Here are some examples of how small changes in the amounts of
nutrients in soil/water can make significant changes in the presence of
plants and animals in the habitat. Generally presence of adequate
phytoplankton in water is good for fishes as they live on these. But when
due to extensive use of fertiliser in agriculture, excessive amounts of
nitrates reach the water system, this causes a sudden outburst of
phytoplankton density in water. This phenomenon is known as ‘algal
bloom’. This dramatic increase in the population of algae depletes the
oxygen store of water so much that, most of the fishes die of asphyxiation.
This is what happened in Lake Erie of U.S.A. in 1960s and 70s. Thus we
find that too much of a good thing may at times be bad as well.
5.2. The great South Bay in Long Island Sound, New York, U.S.A. was a
valuable breeding ground for edible oysters. They had a very profitable
oyster fishery there. Recently large duck farms were established all along
the tributaries leading to the Bay. This led to heavy fertiliser deposits in
the Bay water from duck droppings. The sudden increase in the nutrients
in water resulted into an outburst of some heretofore little known
1. When too much
of a good thing is
bad
2. Ducks vs. Oysters
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Ecology for Millions
flagellates*—Nanochloris sp. and Sticoccus sp. These completely replaced
the indigenous diatom—Nitzschia—which is the normal phytoplankton of
the Great South Bay and food for the famous ‘blue-point’ oyster—the
edible oyster of this Bay. As a result the ‘blue point’ oysters literally
starved to death although their stomachs were full of the new flagettates
(Nannochloris and Sticoccus) which they took in but could not digest.
Nitzschia the normal phytoplankton of this Bay takes in nitrogen from the
watyer only when it is broken down to the state of inorganic nitrates but
the newcomers i.e. Nannochloris and Sticoccus take up N 2 from the
preeceding stages i.e. in the forms of urea, uric acid and ammonia. So
nitrogen is picked up from the water before it become nitrate. Hence
Nitzschia stood no chance. Thus while duck farmers thrived oyster
fishermen starved.
3. Big Chicken and
Clean Bay
5.3. Recently however (1998) there was a heartening report in The
Washington Post, U.S.A., where they have claimed that resulting from
extensive steps that are being taken to reduce the flow of agricultural
wastes in the watershed, the water of the Great South Bay has regained
some of its earlier pristine qualities. This has resulted in the reappearance
of the ‘blue point’ oysters in the Bay raising the hopes of oyster
fisherman. Here is a quotation from a news item in The Washington Post,
12th. Dec. 1998. “Chickens are big business on the Eastern Shore. So is
sea food, bounty of the bay. Not untill a few years ago, however, did
officials realise the connection. The health of this Chesapeake Bay and its
tributaries—and the fish they yield—depends on the care and feeding of
the poultry. Chickens—about 600 million a year—have been sources of
serious nutrient pollution. Federal and State Government have been
working on requirements for controlling poultry pollutants. These
nutrients fuel algae that in turn choke off oxygen in the water and
endanger fish and crabs. “The Washington Post 1998”. Lawmakers have
been seeking to hold big companies responsible for taking the necessary
protective steps. This week to respond to these pressures and to prevent
more government actions, national poultry industry representatives agreed
on a voluntary plan to limit pollution. The industry's acknowledgement of
at least some minimal responsibility for tougher antipollution requirements
is welcome. But federal officials pointed out that the plan falls short of
ensuring that the large companies, not small farmers, would bear most of
the costs.” The Washington Post 1998.
4. Ecological
Indicators
5.4. Some plants and animals respond to the presence of very small
quantities of certain materials present in Nature. For example, pines and
junipers if growing on uranium containing deposits, tend to contain
uranium on the above-ground parts of these plants. If the foilage of such
*Flagellates are a type of one—celled animals (known as PROTOZOA) who are
characterised by the presence of a tail-like structure called flagellum along with their
bodies. Example-malarial parasite—Plasmodium sp.
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plants are examined (fluorimetrically) and found to conotain more than 2
ppm uranium, the soil is considered to contain commercially exploitable
deposits of uranium. Hence here pines and junipers can be called as
ecological indicators of uranium in soil. Similarly, caged small birds are
sometimes lowered into mine shafts to test the quality of air inside deep
mines. These are very sensitive to oxygen depletion so, quickly dies if O2
content of air is less than normal.
5.5. A general observation. From the above few examples and many
other situations it may be broadly concluded that the ‘steno’ species, (and
not the ‘eury’ species) i.e. those species whose capacity to tolerate
changes in a particular factor in the environment is very narrow, or
limited, are better indicators of environmental quality.
6. SOME IMPORTANT PHYSICAL FACTORS' ROLE IN
INFLUENCING PRODUCTIVITY
Now we shall discuss very briefly the roles played by some very
important physical factors on the survival and growth of populations.
6.1. TEMPERATURE
Living beings
within this
range only
6.1.(1). Temperature is a very important regulatory factor for the survival
and growth of all living beings on earth. The temperature on Earth can
range from hundreds of degrees centigrade in magma (the fluid core of
Earth) to –70/80°C in polar caps. But living beings as a whole can only
live within a small part of this range, say + 90 to –190°C. Again no
organism of any particular species can survive, grow and reproduce
throughout this entire range of temperature but only within a much
shorter band of this range which varies from species to species (Fig.
III.6).
–273°C
–100°C 0°C
200°C
400°C
600°C
800°C
1000°C
9000°C
11,000°C
3000°C
0° Kelvin
Temp. in the
surface of the Sun
(10,000°C)
Figure III.6 Scale of Temperature within our Solar system.
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Ecology for Millions
6.1.(2). Interestingly the range of temperature which can be
tolerated by a species not only varies from species to species but
within the different stages of life cycle of the same species. Each
stage of the life of a species can live only in a much narrower band of
the overall range ot temperature tolerable to the same species. This fact
often acts as limiting for the survival and growth of a species. Anybody
who is observant and have some experience of Nature must have noticed
that a sudden and unexpected rise or fall in atmospheric temperature will
result in the abundance of some species of plants or animals of the place.
There may be an outbreak of pests or disappearance of pests or
flowering may be delayed or hastened. Owing to such fluctuations in the
incidence of insect pests, the yield of cash crops which are affected by
such pests, will also fluctuate. Generally metabolic activity is directly
related with temperature. Stored grain pests particularly, grow faster in
higher temperature. Larvae or Tenebrio molitor, (a stored grain pest) grow
much faster in summer than in winter when the temperature drops
considerably. Similarly development of eggs of grasshopper Austroicetes
cruciata show almost a curvilinear relationship with the rise of
temperature, from a threshold of 16°C till about 36°C (Fig. III.7).
Ambient temperature
and survival
6.1.(3). When body temperatures of animals is compared with those of
environments we find that some animals such as birds and mammals
maintain a constant body temperature irrespective of the temperature of
the environment while others such as, fishes, amphibians (frogs and
toads) and reptiles' body-temperature rises and falls along with
Classification of
organisms on the
basis of their body
temperatures.
ENDOTHERMS
and ECTOHERMS
Development (% day)
28%
20%
12%
4%
8°C
16°C
24°C
32°C
40°C
48°C
Temperature (°C)
Figure III.7 Development of eggs of grasshoppers— Austroicetes cruciata
is nearly linear between 16° to 36°C
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temperature of the environment. The first group is called endotherms
and the second group is called ectotherms.
“Endotherms regulate their temperatures by the production of heat within
their bodies ; Ectotherms rely on external sources of heat." (Begon,
Harper and Townsend, 1990, p. 48). (Quotes are author's). Earlier the
endotherms were called homoiothermic and ectotherms poikilothermic.
There are however some differences in the precise meanings between
these two sets of terms. But the aim of this small book does not warrant
such refinerments. We may even use a still simpler set of words without
losing much. These are wormblooded for endotherms and coldblooded
for ectotherms. (Recently biologists have found that some endotherms can
alter their body temperature to suit their situations).
6.1.(4). Most places in Earth experiences seasonal changes in temperature.
Organisms living in a particular place have to cope with its temperature.
Generally this is done in one of the three following ways :
(a) Behavioural adaptations
(b) Anatomical changes and
(c) Physiological adaptations.
Here are a brief account of these.
a. Behavioural Adaptations. Animals tend to move into and away
from places of favourable and unfavourable temperatures respectively.
Basking in sun by grasshoppers, crocodiles and snakes etc. are temperature
adaptations by cold blooded animals. Birds mostly fly about in mornings
and evenings when the air is cool and rest in shade during mid-days which
are hot. In winter mornings grasshoppers after crawling out from under the
grasses, perch on the grass-tips placing their broad-sides towards sun and
thus absorb maximum solar radiation. After absorbing enough heat they
start hopping about. Again during mid-day, if it is very hot, grasshoppers
will either hide under grass or sit putting their heads towards the sun so as
to absorb minimum heat. In winter crocodiles mostly sit on the riverbanks
basking. During spring and winter rattlesnakes in North America regularly
bask on rocks. Trees however being rooted have little scope of such
dynamic behavioural adaptations. The leaves of some plants hang down
during mid-day to avoid too much heating and the resultant water-loss from
transpiration through leaves. Most trees however have thick barks to
protect these from extreme heat or cold.
b. Anatomical Adaptations (changes). The most dramatic
anatomical adaptations are found in the hearts of vertebrates (animals with
backbone). The endotherms (birds and mammals) have a four-chambered
heart. The ectotherms have either a three-chambered heart (amphibians
and reptitles) or a two-chambered heart (fishes) Figure—III.8. Here is a
brief explanation. Broadly vertebrates can be either completely aquatic like
fishes or partly aquatic or partly terrestrial like amphibians or fully
Devices for coping
temperature
variations
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Ecology for Millions
(d)
In Birds and
Mammals–fully
four chambered
Left auricle
Right auricle
Left ventricle
Right ventricle
(c)
In Reptiles
partially four
chambered
Left auricle
Right auricle
Left ventricle
Right ventricle
Septum
(b)
In Amphibians:
three chambered
Left auricle
Right auricle
Ventricle
Sinus venosus
(a)
In Fishes: two
chambered
Auricle
Ventricle
Conus arteriosus
Figure III.8 Evolution of Heart in Chordata.
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terrestrial like reptiles, birds and mammals. Fishes and amphibians are
ectotherms while birds and mammals are endotherms. The reptiles are of
intermediate type. The anatomy of the hearts of each of these group are
also quite distinct.
b.(i) The simple and small hearts of fishes consist of only a series of
four linearly arranged chambers through which only non-aerared blood
flows. These chambers are, starting with the fish—sinus venosus, auricle,
ventricle and conus arteriosus (Fig III.8a). In fish deoxygenated blood
from the entire body returns to the sinus venosus and moves on through
the auricle to the ventricle. The ventricle pumps the blood through the
conus to the ventral aorta from where blood flows into the gills for
oxygenation. Then this oxygenated blood flows through the body
providing oxygen to the tissues and finally returns to the sinus venosus
deoxygenated. The cycle is repeated again and again as long as they live.
b.(ii) The next higher group are amphibians, who have lungs for
aerial respirations, have developed a partition in the auricle making it two
chambered—right and left auricles. So instead of one auricle and one
ventricle, an amphibian heart has two auricles and one ventricle i.e., it is
a three chambered heart. The right auricle receives the deoxygenated
blood from the body while the left receives the oxygenated blood from the
lungs. But in the next chamber—the ventricle as it is unpartitioned, the
oxygenated and deoxygenated blood gets somewhat mixed but not fully
(Fig. III.8.b.). When the ventricle pumps the blood forward, owing to a
special septum* in conus arterious, the relatively less oxygenated blood is
guided to lungs for oxygenation and the more oxygenated blood is sent
into the body. Thus in amphibians we first come across the beginning of
a double circuit heart which keeps the deoxygenated and oxygenated
bloods somewhat separate and send these into two directions—
deoxygenated to lungs and oxygenated to body. Still the amphibians’
bodies do not receive fully oxygenated blood but only a mixture of
oxygenated and deoxygenated. Hence they are cold blooded or
ectothermic. That is why amphibians can stay only in warm places.
b.(iii) Amongst the fully terrestraial vertebrates such as reptiles,
birds and mammals, the ventricle too is devided into two chambers. So
now there are four chambers—two auricles and two ventricles and hence
the oxygenated and deoxygenated bloods do not mix any more.
Deoxygenated blood from the body enters the right auricle and thence to
the right ventricle from which it is pumped into the lungs for oxygenation.
The oxygenated blood from the lungs returns to the left auricle and from
there to the left ventricle. The left ventricle pumps the oxygenated blood
to the body from which the spent blood returns to the right ventricle. The
cycle begins again (Fig. III.8.e). Owing to the presence of two auricles
*Septum—partition; a deviding wall
Anatomy of Heart
and Body
Temperature
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and two ventricles in the hearts of birds and mammals, the oxygenated
and deoxygenated bloods remain separate throughout their flow through
the heart. That is why such hearts are known as double circuit heart.
This is the basis of their warm bloodedness and hence they are called
endothermic. So they can stay both in cold as well as warm places.
(Reptiles' hearts are only of intermediate type between amphibians in one
side and birds and mammals in other side).
Insulation and Body
Temperature
b.(iv) There are many other anatomical features which reflect
remarkable adaptations to ambient temperatures. Here we shall briefly
touch upon only two. Blubber : In order to retain the body-heat mammals
living in the freezing arctic zones develop especially thick (3-6") layer of
fat under their skin. This thick fat layer is called blubber. Polar bears,
seals, whales living there all have bludder. These thick blubbers yield so
much of oil that Eskimos use this oil to light lamps in their igloos.
Feather: Bird feather is a specially structured insulating device. Feather
not only prevent heat from escaping from the bodies of birds' in winter,
these also keep the high heat of summer out. The soft belly feather of
Eider ducks which are known as down feathers are used as stuffing for
quilts and pillows for use in extremely cold places.
c. Physiological Adaptations. Physiological adaptations to inclement
temperatures are equally interesting and variegated. Neverthless for the
sake of brevity and conforming with the aim of the book we shall mention
only two.
c.(i) Hibernation : This is a state of dormancy adopted by some
vertebrates to tide over severe winter conditions. Some amphibians,
reptiles and mammals hibernate during winter. Before the onset of winter
such animals eat plenty to accumulate fat in their bodies. During winter
amphibians and reptiles enter into a safe hiding place, become dormant
and wait for the return of spring when their body become warm enough
enabling them to move about. Mammals such as, bears, rabbits hamsters
who live in places which become snow-covered during winter mostly
hibernate. When snowfall sets in bears enter into specially prepared dens,
curl up and enter into a deep winter sleep. They come out of their dens
lean and hungry only in the beginning of spring. Other hibernating
mammals also follow more or less the same pattern of hibernation. During
hibernation to conserve energy store of body, both the heart-beat and
body-temperature drops severely. For instance, the heart-beat of hamsters
(a type of squirrel) drops from 110 to 10. Metabolic activity too is brought
down to a minimum. This is just as well as, the lower the heart-beat etc.
the lesser the need to generate heat by burning fat.
c.(ii) Aestivation : While hibernation is a device to tide over severe
cold, aestivation is a device to tide over severe summer heat and
drought. Dipnois or fishes with lungs, adopt this. Lung-fishes are natives
of Australia, South-west Africa and South America. Protopterus sp. a
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lung fish live in the shallow swamps of Afrika. During summer most of
such swamps dry up. So during summer Australian lung-fishes i.e.,
Protopterus sp. aestivate. Just prior to the onset of summer draught
Protopterus enters into large egg-shell like cavities, well under the mud
bottom, secrete senough mucilege and curl itself up within a cocoon of
mucilege lodged safely under the mud bottom and wait till the return of
rains (Fig. III.9). This over-summering device is aestivation.
Respiratory Tube
Cocoon
Mud housing of
the cocoon
Protopterus aestivating
within a waterproof cocoon
Figure III.9 A Protopterus (lung fish) aestivating during summer.
6.2. LIGHT
2.0. Sun Light is a crucial ecological factor. Without sunlight all the
pulsations of life will cease and then in very short time our lovely and
living Mother Earth will turn into a barren LIFELESS mass spinning
around sun like other planets.
2.1. Sunlight supplies the energy required to synthesise biomolecules by
green plants using simple inorganic molecules—CO2 and H2O. Green
plants do so by trapping solar energy with the help of their green
pigment—chlorophyll. This synthesis of biomolecules by green plants
using solar energy is known as PHOTOSYNTHESIS. The quantity of
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Ecology for Millions
solar energy thus trapped by green plants is the ultimate source of all
energy used by all other types of living beings including human beings, all
over the world. Thousands of years ago the Vedic philosophers of India
rightly understood the significance of SUN and praised him as the ultimate
saviour of the world.
2.2. Here is a simple formula showing how much solar energy is trapped
into a biomolecule through photosynthesis.
6CO2 + 6H2O + 709 kcal ------- 6O2 + C6H12O6
Here the quantities of inorganic compounds are in terms of moles* and
energy is in terms of kcals** Green plants are the only group of living
beings who can prepare their own food trapping sun's energy. This is why
green plants are called autotrophs. These biomolecules when break down
release the solar energy trapped inside which is then used to power all the
subsequent biochemical reactions inside a living body. Thus sun is the
ultimate source of all biological activities on earth.
2.3. The electro-magnetic waves which emanate from the sun are mostly
lethal to life. Most of it is stopped by the upper layers of earth’s
atmosphere and only a fraction of it which is visible light reaches, the
surface of earth. This visible light which again consists of only a small
range, beginning with a fraction of ultraviolet and ending with fraction of
infra red light, is the energy source of all the photosynthesis and other
biological activities on earth (Fig. III.10).
Solar energy and
visible light
VIBGOR
VIBGYOR
X rays
U.V.
Transmission
factor
g rays
10
–10
10
6
V
I
S
I
B
L
E
–4
10
Visible
light
Radio
Infrared
Earth’s
surface
10
–2
2
10
10
4
Outermost
layer of
10
earth’s
atmosphere
6
Figure III.10 The relative transmission of solar radiation from the outermost
layer of Earth’s atmosphere to the surface of earth.
*Mole: That amount of a substance whose weight equals to its atomic weight in
grams.
**Kcal: One thousand calories (calorie is an unit of heat).
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2.4. Photosynthesis is mostly limited to visible lights which has a
wavelength range from 400 (near U.V.) to 750 (near I.R.) microns***.
The rate of photosynthesis however varies somewhat with the wavelengths
of visible lights (violet, iindigo, blue, green, yellow, orange and red). (This
set of visible light is briefly named as ‘VIBGYOR’). In terrestrial
locations the colour composition of light does not vary much but in
aquatic situations it is not so. In deeper waters reds and blues are filtered
out and the resultant greenish light is left for chlorophyll for
photosynthesis. So as an adaptation to life in deeper waters, the red
marine algae have developed supplimentary pigments—phycoerythrins
which enable these algae to live in deeper waters.
2.5. Photosynthesis depends upon besides colour of light (wavelength),
also on intensity of light (foot candle) and duration of light (day length).
Unlike rainfall which may vary from year to year, in the same location,
sunlight for a particular location remains unchanged from year to year.
Both in land and in water photosynthesis increases with the intensity of
light but only up to a point after which, it decreases. Actually at high
intensities of sunlight photo-oxydation of enzymes reduces synthesis. This
is why in full sunlight, marine phytoplanktons move down from the
surface of the sea to the deeper waters. In forests as trees cannot move
about, these adapt to different intensities of sunlight according to their
locations in the forests. For example, young seedlings of pines are shade
adapted but the older seedlings which are taller, are unable to survive
under a canopy.
53
Wavelength of light
and photosynthesis
Photosynthesis Role
of Light and Heat
2.6. Just as too much sunlight is limiting to photosynthesis so is heat. An
interesting example are orchid flowers. In nature these grow in colder
places under shades. But it has been found that orchids can grow quite
well in sunlight, if temperature can be kept low. So now-a-days orchidgrowing in temperature controlled green houses is a good business in
many countries. In India too orchid growing can be a good business.
2.7. Duration of sun-light or day-length controls many biological events.
Activities such as flowering of plants, seasonal migration of birds, laying
of eggs by birds, insects etc., and many other activities are regulated by
day-length (or in some cases the reverse of day-length i.e., length of darkperiod). The reason behind this linking such biological activities with sun
light is not difficult to understand. Sunrise and sunset are the most
dependable natural qualities of a particular location of earth. So if,
biological events are timed by day-lengths, rarely will these fail to meet
the needs of Nature. For instance, birds time their egg laying in such a
season when the fledgelings will have maximum chance of finding food
and hence survival. So do insects, so do plants, so do fishes and many
other living beings. Sir David Attenborough the renowned biologist in his
***A micron µ is 1/1000 of a mm. and a m µ (millimicron) is 1/1000 of a micron.
Photoperiodsm or
Ecological clock
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Ecology for Millions
beautiful book ‘The Trials of Life’, 1990. page 11-14, has described very
touchingly the phenomenon of egg-laying by land crabs (Gecarcoidea
natalis) of Christmas Island in the Indian Ocean, during a particular
season. Here are a few lines from him. “Soon the sea is fringed with a
moving scarlet carpet of glinting shells, grappling legs and craning sticklike eyes. When at last the waves sluice over them, each shakes her body
convulsively so that the brown eggs swill away in the water and, with a
touching gesture of apparent exultation, lifts her claw above her head as
if waving a salute.”
2.8. With growth of our knowledge about photo-periodism many specific
terms have been introduced to denote specific situations or responses for
specific animals and plants. Diapause for insects, Aestivation for lungfishes, Hibernation for mammals, reptiles and amphibians and Seasonal
Migrations for birds and whales etc. are various types of physiological
adaptations meant to synchronise Life with Rhythms of Nature. Such
adaptations which are also known as Environmental Clocks are imprinted
in the genetic make-up of animals and plants and animals who adopt
these, can follow the pattern unerringly throughout their lives.
2.9. The study of photo-periodism is a relatively new but fast growing
area of biology. Commercial breeders are programming the breeding
seasons of fishes and poultry in such a way so that their profit margin
goes up. This they do by manipulatiing day-length with artificial light
(Fig. III.11). Now-a-days poultry owners routinely do this. Such
techniques are now being adopted for flowering plants as well other
animal species.
Normal
light
16
Artificial
light
8
Jan.
Mar.
May
Jul.
Sept.
Nov.
Figure III.11 Control of breding of brook trouts by artificial lighting.
6.3. WATER
3.0. Water or Moisture is another crucial ecological factor. Although
essential for survival and growth nevertheless the quantity and quality of
water available in different habitats poses various types of threats. Such
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threats lead to adaptive radiations (i.e. adaptive changes in the structure
and physiology leading to speciation*).
3.1. Animals living in fresh waters have to tackle the ingress of too much
of water into their bodies while reverse is the problem in saline waters
(seas). The Osmotic pressure of fresh-water being very low and that of
body fluid much higher, water tends to enter into the bodies of fresh water
animals while, the osmotic pressure of sea-water is higher than the body
fluid of animal living there ; hence marine animals tend to lose water in
salt water. So from the point of view of water-balance in the body fluid of
animals, fresh water is too wet and sea is too dry. Sea may be likened
with desert. Brakish waters (waters in river deltas opening into seas)
present a situation intermediate between freshwater and marine. Such
borderline habitats are usually very rich in variety of liviing beings as
these have a variety of microecosystems.
3.2. In brakish water ecosystems, specially in river deltas, like Sundarbans
of Bengal, where large tracts of inter-tidal zone with muddy soil prevail,
a special type of plants grow. These have special air—breathing roots—
pneumatophores, which stick out vertically from mud flats to breathe air
when tidal water recedes (Fig. III.12.). This unique device is developed by
a number of species of such habitats. Such species occupy and prosper in
tidal zones. In this way hundreds of square kilometres of intertidal zones
have been afforested all over the world. Thus grew mangrove ecosystems.
The world famous abode of ‘Royal Bengal tigers’ the Sundarbans of
West Bengal and Bangladesh is thus created by Nature in the mouth of
the river Ganga. Mangroves are extremely rich in food materials and
because of its intertidal nature and forests, the mangroves have become
the breeding ground of many important species of prawns and fishes etc.
Besides fishery and tigers, the Sundarbans is also the abode of deers,
crocodiles, and many other important species of fishes and bees etc.
3.3. These mangrove ecosystems not only protect the coastal areas from
the severity of storms and cyclones but also help to extend the forests of
the deltas. Unfortunately however human greed for quick profit has
resulted in extensive destruction of mangroces in West Bengal and Orissa.
The recent ravages suffered by Orissa from cyclone (Oct. 1999) is
particularly aggravated by the destruction of the mangroves of Orissa
coasts. This cyclone has harmed commercial breeding of prawns. In India,
K.R. Naskar is engaged in an in-depth study of Sundarban ecosystem
particularly its flora (2004, Manual of Indian Mangroves p. 1-220, Daya
Publishing House, New Delhi—110 002).
*Speciation: The biological process of evolution of a new species. (Evolution and
speciation of Darwin's finches in Galapogos Islands is is very good example of
speciation. Even to-day new specis of finches are evolving there).
Mangroves and
protection of sea
coasts
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STAGE – I
12"
A seedling
STAGE – II
A young sopling
Pneumatophores
STAGE – III
A small tree with
pneumatophores, stilt
roots and seedlings
Stilt root
Figure III.12 Mangrove plants with their pneumatophores.
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3.4. The nature of the terrestrial ecosystems mainly depends upon two
things:
(a) amount of rainfall per year and
(b) how the rainfall is distributed over the year.
Roughly, depending on the total amount of rainfall per year, ecosystems
can be grouped into four types.
I. Desert—
0-10´´ per yr. (Sahara of Africa, Thar desert
of India and Pakistan)
II. Grassland/Savanna—10-30´´ per yr. (Serengeti National Park of
Kenya)
III. Dry Forest—
30-50´´ per yr. (Rajasthan and Madhya
Pradesh of India)
IV. Wet Forest—
50´´ and above per yr. (Congo watershed of
Africa, Sub-Himalayan forests of India and
Amazon forest of Brazil).
There are more example of each type. There is however one important
point to remember. The above classification is based only on the total
rainfall in a year, irrespective of distribution of this rainfall over the year.
Rainfall, even relatively low—for instance 30" if distributed more or less
evenly over the year can support a nicely woody ecosystems and
beautiful glens as in Gt. Britain but if, it is concentrated to only 1 to 2
months of the year, this will invariably lead into a savanna type ecosystem
as in Africa.
3.5. The retentivity of rainwater by soil is another important point for
plant growth. Clay soil can retain more water than loam soil and loan soil
more than sand soil. For agriculture loam soil is most suitable as, it is
both porous and hence facilitates breathing of air by plant roots and also
it can retain enough moisture for good plant growth while, clay soil tend
to become too hard for roots and sandy soil looses moisture too soon.
5. RAINFALL AND TEMPERATURE ACTING TOGETHER
5.0. Right amount of water and right amount of heat are musts for every
living being for its survival and prosperity in a place. The only exception
to this rule are the human beings (Homo spaiens) who through their
unique quality—the power of thinking, have created artificial
environments which they can carry along with them (clothings) and thus
occupied every corner of earth.
5.1. The effect of humidity and temperature are however interlinked. The
effect of a particular amount of water in a place at a particular
temperature say ‘x’ will be quite different in the same place with the same
amount of water but at a different temperature say ‘y’. This is because
the warmer a place is the quicker water tends dry up in that place. Here
is an example.
Nature of Soil and
Humidity & plant
growth
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Let us take four chambers all 1 litre each and all containing 20 cc of
water each. Let us keep these four chambers at four different
temperatures—. These are 10°C, 20°C, 30°C, and 40°C. Now let us
examine the relative humidities in each of these four chambers
(Fig. III. 13.).
10 cm
10°C
RH = 100%
VPD = 0 mm
1 litre
air in
each
10 cm
20CC
WATER
10 cm
20CC
WATER
RH = 66%
VPD = 10 mm
10 cm
30°C
20°C
RH = 100%
VPD = 0 mm
10 cm
20CC
WATER
10 cm
10 cm
20CC
WATER
40°C
RH = 50%
VPD = 20 mm
10 cm
Figure III.13 Changes in the R.H. (relative humidity) and VPDs (vapour
pressure deficits) of same enclosed spaces at different
temperatures but containing same amount of water.
5.2. One litre of air at 20°C can hold a maximum of 20 cc of water
when the relative humidity (R.H.) would be 100%. But at 10°C it can
hold only 10 cc of water; so the R.H. will not only be 100% but the
chamber will also contain 10 cc of liquid water as dew. Similarly to be at
100% R.H. the chamber at 30°C will need 30 cc and at 40°C will need
40 c.c. of water. Therefore the relative humidities of these chambers
which all containt same amount of water i.e. 20 c.c. each, but are at
different temperature i.e. 10°C, 20°C, 30°C and 40°C will be 100%,
100%, 66% and 50% respectively. This means that at lower temperature
air with same amount of water will be saturated and the extra water
vapour will settle as dew while, at higher temperature the reverse will
happen—the air will be relatively dry so, the plants may suffer from
draught. Therefore the effect of water vapour on an ecosystem is
intimately associated with the ambient temperature of that place.
Climograph
5.3. Considering the above points it is now generally accepted that an
overall combined picture of rainfall and temperature of a place would be
a very useful guide for agriculturists. Climograph gives such a picture. A
climograph is a two dimensional graph giving the rainfall and temperature
of a place as monthly averages (Fig. III.14.). If the climograph of a
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80
7
8
6
7
60
6
10
9
Moisture
5
10
40
4
11
20
Missouri
9
8
A
3
4
B
3
11
12
5
European
optimum
C
Montana
2
1
12
2
0
1
2
Temperature
4
6
Figure III.14 Temperature-Moisture climographs of three places.
district is compared with that of another district one gets a very good idea
regarding the suitability of a place about the cultivation of a particular
crop. Thus climograph which sumarises two important parameters of
climate of a place, over the year, helps us to guess intelligently the
likelihood of success of an imported species to be established in a place
or not.
5.4. Summing up: So far we have discussed very briefly, four important
environmental factors which play crucial roles in determining success of
a species—in fact any species—in a particular habitat. These factors are :
1. Temperature
2. Light
3. Water
4. Rainfall and Temperature acting together.
This list is not all. There are other factors which also play important roles.
Some of these are soil and its pH, air current and pressure,
microenvironments and pollutants etc. Although these are important
considerations neverthless considering the scope of this small book we are
leaving out this rather vast area of information. The book is for 'millions'
so kept limited to basics.
6. ECOLOGICAL NICHE (THE HUTCHINSON CONCEPT)
6.0. We however have got enough exposure regarding the role of
environment on population to introduce a very important ecological
concept—Ecological Niche.
6.1. The term ‘Ecological Niche’ is in vogue for more than half a century
but only much later a more precise definition emerged. Broadly, ecological
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Ecology for Millions
niche means the sum total of the limits of various environmental factors
within which a species can successfully survive, breed and prosper to
maintain a stable population.
6.2. Let us examine this statement a bit closely. A species may be able to
tolerate a very wide range of temperature of which a relatively narrow
band would be suitable for breeding, an wider band for growth and the
entire range for the survival of the individuals (Fig. III.15). This is a
simple graph—a line. But as we have discussed earlier, the combined
effect of temperature and humidity would mostly result into a narrower
range for survival (Fig. III.16). This is a two dimensional figure - an area.
If another factor for instance current flow, is also brought into
consideration than the range which would be found suitable would be
even narrower (Fig. III.17). The situiation depicts a three dimensional
figure—a volume.
Various life processes of a species
of their specific needs of temp.
Temp.
Breeding
possible
Individuals
can grow
Individuals
can survive
Figure III.15 Range of temperatures which a species can tolerate.
Hutchinson concept
of Ecological Nichea n-dimensional
hypervolume
6.3. In Nature however in order to breed, survive and maintain a stable
possible population a specied has to face several factors such as,
temperature, humidity, air current, salinity of soils, minerals, sunlight and
so on. Each factor will impose its own limitations on the range. The
combined effect of all these factors determine the effective or realised
niche or ecological niche of a species. Therefore the true 'Ecological
Niche' can be thought of as an n-dimensional hypervolume within which
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61
Humidity
Productivity
Effective range
for survival
Temperature
Humidity
Cu
rre
nt
/fl
ow
Figure III.16 Effective Range for Survival when temperature
and humidity are considered together.
Temperature
Figure III.17 A three dimensional Ecological Niche.
the species can maintain a viable population (Begon et. al. pp. 76). This
concept was first proposed by G. E. Hutchinson in 1957. Since then it is
known as Hutchinson concept of ecological niche. More about this will
come later.
7. ERAS OF HUMAN CIVILISATION
Rise in Productivity and Human Population
7.0. Since the dawn of human civilisation plants are intimetely involved
with its growth and spread. Civilisation has four distinct chronological
phases. The earliest phase is the stage of the Hunters; the second phase
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Ecology for Millions
is the phase of the Pastorals; the third phase is the phase of the
Agriculturists and the latest phase is the Industrial phase i.e. the phase
of today.
The Hunters
7.1. The Hunters mostly lived by hunting animals and on fruits and roots.
Meat was their main food and hide their raw material for clothings, huts
and lining of the caves. The bones of animals were used as tools. Hunters
also used to eat roots and fruits as and when they found these. Hunters
scarcely affected forests. Even today some of the Australian natives live in
this way. Hunters who drew the beautiful rock paintings of bisons in the
caves of Altimara reindeer herds in Castelon, Spain are glorious example
of their culture - which flourished about 20,000 years ago.
The Pastorals
7.2. The people of the second phase i.e. the Pastorals learnt to
domesticate some animals mostly cows , horses and dogs. They used to
own huge herds of such animals and moved then for grazing, from
season to season over vast tracts of land. Even today there are some wellknown pastoral people. Some people of Mongolia are horse herders;
Bedouins of Arabia are camel herders ; Lapps of Northern Scandinavia are
reindeer herders. Pastoral people follow their herds as these move from
place to place in search of grazing ground. Pastoral people too did not fell
forests. Such people meet most of their daily needs from their herds—but
not all. Tea which is a product of agriculture is used regularly by many of
presentday herdsmen.
The Agriculturists
7.3. The third phase people the agriculturists came next and formed bases
of predominent human civilisations all over the world. The Agriculturists
owing to their dependance on cultivating selected plants in continuous
areas, had to fell forests extensively to do so. Today in some areas of
U.S.A. and Canada there are miles and miles of continuous tracts covered
with corn or wheat only. Most people today are dependant on agricultural
products. Many of the beautiful edifices such as the magnificient
pyramids of Egypt, beautiful temples of South India and gorgeous palaces
of Europe are products of agricultural societies.
The Industrialists
7.4. The fourth and the latest phase is the Industrial age. In many places
of today's world we find an admixture of agriculturists and industrialists.
In fact these two phases have become interdependent. In this stage Mother
Nature is being exploited most ruthlessly and most extensively by using
highly sophisticated tools for both animal husbandry as well as
agriculture. No part of Earth today, which were earlier left alone for their
apparent inaccessibilities, be it freezing arctic, be it scalding desert, be it
mosquito-infested swamp, are any more safe from the prying eyes and
greedy fingers of today's men—Homo sapiens.
7.5. As one civilisation succeedes another, mens' power to extract more
food from the same area increased and so did human population (Fig. I.1
and Fig. III.18 and Table I.1). Consequently from five million or less,
about 10 to 12000 years ago—at the dawn of civilisation, today, human
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63
4000
Human population
(in millions)
3000
2000
Agriculture
&
Industry
1000
Hunters
12000
10000
Pastorals
8000
Time (yrs.)
Before present
6000
Industrialists
Agriculturists
4000
2000
B.C.
Present
Figure III.18 Growth rate of human population over the last 12,000 years.
(Partly from Atlas of World History Harper Collins 1978, p. 36 and
Environmental Geology. A.E. Keller, 2002, p.10, Prentice Hall.)
population has surged to a staggering 5000 million or more ! No corner of
Mother Earth is safe from loot by us. This horrendous growth of
population of Homo sapiens must be stopped and our population should
be reduced to a level, we believe, of 1000 million or so for the entire
world. Otherwise our doom is not far. India for example, should reduce
her (and also for all countries with such populations) to 200 million or so
and China to about 300 million or so. Till this is achieved we fear, the
quality of life of these densely populated countries would always remain
low in comparison with land-rich Euro-American and Australian people.
To-day the entire world must stand hand in hand to fulfil this aim.
7.6. One of the several damages this spurt in human population growth
has caused to Earth is disturbing of the water-balance of soil. Normally
rainwater falling on forests or grasslands mostly gets absorbed into soil
before the surplus water runs off into the rivers, lakes and seas. Owing to
this, very little soil would be washed into the rivers. So the soil erosion
would be minimal. But when trees are felled extensively to make way for
vast agricultural tracts, rain water which hit the bare agricultural fields
with loose and tilled soils, would quickly be washed into the rivers
carrying huge quantities of top soil with it. (Table. II.1.). As a result of
this washing off of the top soil into rivers and seas during monsoons, at
Civilisation and
growth of Human
Population and the
ills that are following
Agriculture and
Soil Loss
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least three damages occur. (a) As water quickly runs off into the sea,
adequate rainwater does not enter into the deeper layers of the soil to
recharge ground water. Hence ground water level gradually goes down,
trees suffer, wells dry up and arsenic poisoning of well-waters shows up
(explained earlier). (b) As top-soil from agricultural fields deposits into the
river beds as silt, gradually the river beds become raised and so their
water bearing capacity get reduced. Hence during monsoons rivers easily
spill over the embankments and flood extensive areas. (c) As water
bearing strata of soils (aquifers) slowly dry up even the forest ecosystems
begin to suffer.
Importance of
water management
Water is a precious commodity. Our planners must realise this and,
take ecological principles into consideration while planning, carefully plan
water-management and also ensure that the plans are implemented
properly, regarding always water as a precious commodity.
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Chapter IV
Bioenergetics
(Sun the Ultimate Source of Energy of Earth)
Topics
IV.1. Importance of Sun
IV.2. The Basic Principles Involved
IV.3. Light and Photosynthesis
IV.4. Energy Circuits
IV.5. Standing Crop, Carrying Capactity & Productivity
IV.6. Percentage of Solar Energy Used and World Productivities
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intentionally left
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CHAPTER 4
BIOENERGETICS
(Sun the Ultimate Source of Energy of Earth)
— from Vedas—a mantra on worship of sun
*
*
*
*
*
*
— from the poem “Ode to Trees” in the book “Banabani”
by Rabindra Nath Tagore.
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1. IMPORTANCE OF SUN
1.1. Sun is the ultimate source of all energy of our Mother Earth. Not
only the photosynthetic productions of all biomaterials of all ecosystems
are powered by solar energy, but such spectacular sights such as, the
giagantic Niagra Falls of U.S.A. pouring down 800000 gallons of water
per second or the devastating hurricane like Mitch near South America or
the horrible cyclone in October 1997 hitting the Orissa coast of India or
the chilling landslides in Himalayan glaciers or the scalding and massive
volcanic eruptions of Pina Tibu etc. all are powered by solar energy.
1.2. This section of this simple book will be devoted to an attempt to
understand how solar energy powers ecosystems. A proper understanding
of this process is vital for the survival and prosperity of mankind without
causing irrevocable damages to our ecosystems.
1.3. Untutored though they were of modern experimental sciences, the
ancient sages of humanity rightly guessed the importance of Sun in their
lives. Sun was the most benevolent god to them and they wrote beautiful
verses in praise of Him. The Sanskrit verse given in the begining of this
chapter is from ‘Vedas’ (which is one of the two important books on
Hindu philosophy)—written well over 4000 years ago. This sanskrit verse
is recited even today in all Hindu religious ceremonies. This verse
describes the resplendent beauty of Sun and His effects on our lives in
just four exquisitely beautiful sentences.
1.4. The ancient Egyptians of the days of Pharaohs worshipped Sun as a
god - the god RA. To them it is the sun-god RA who through his
benevolent hands constantly showers blessings on his devotees in the form
of food grains, cotton and all other things that they need (Fig. IV. 1.).
Such beliefs were shared more or less by most ancient civilisations. The
Hindus called the Sun god as / ‘ARKA’ / Or SURYA DEVATA, (there are
SUN
Sun s hands
of blessings
Figure IV.1 The sun god– “RA” of ancient Egyptians with his hands of blessings.
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many other names as well). The religion of ancient Persians grew around
Sun. In fact still today, Persians who are not converted to Islam, call
themselves sunworshippers.
2. THE BASIC PRINCIPLES INVOLVED
2.1. First the solar energy is picked up by green plants. This energy
locked into plants’ bodies is passed on from them into animals providing
energy for all their biological activities. Again as wood, coal and
petroleum, plants provide energy for all other activities responsible for
sprouting up and spread of human civilisation in its breath-taking
splendour of today. This phenomenon has been beautifully described by
the Indian poet Rabindra Nath Tagore in the second poem quoted in the
beginning of this chapter. He said “Oh trees, by lending the power which
you have drunk from the Sun, to men, you have made them so strong that
they have conquered the Earth and now they are trying to challenge God
himself”. (The preceeding lines within italics are author’s own translation
of a part of this poem in an attempt to depict the spirit of this superb
poem). This forms part of the 2nd poem in the begening of this chapter.
2.2. The properties of energy can be understood by following the basic
laws of thermodynamics.
2.3. The First Law of Thermodynamics states that energy can neither be
created nor destroyed; it can only change from one state to another. For
example, from light to heat etc. When sunlight falls upon a surface it
warms up the surface, which means light is converted to heat. There are
many such examples.
1st Law
2.4. The Second Law states that at every step of conversion i.e. change
from one state to another some energy will be invariably lost (or
dissipated) into the environment. Consequently energy will always flows
from a higher level to a lower level (Fig. IV. 2.).
2nd Law
2.5. The Third Law states that Nature if left to herself tends to lose
energy and thus gradually sink to more and more disorder. In
thermodynamics this is known as entropy i.e. a “hypothetical tendency
for the universe to attain a state of maximum homogeneity in which all
3rd Law
EN
Level-1
Level-2
Level-3
Level-4
Sunlight
VI
RO
NM
Heat
EN
T
Electricity
Heat
Figure IV.2 Loss of energy to environment (also called
‘heat sink’) at every change of its form.
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matter is at a uniform temperature” (Webster’s College Dictionary). In
short, third law implies that without constant input of energy order tends
to disorder. (It seems to me this is the likely reason of our finding so
much of chaos and disorder and decay in societies where men are not
very energetic, disciplined and orderly).
Death and Decay
2.6. The decay of bodies after death can be easily understood through
this third law. To remain alive a living being requires constant input of
energy. This energy is obtained through respiration followed by several
subsequent metabolic processes. If the respiration is stopped then, soon
the animal dies. The same thing happens with waterlogging of plant roots.
After death when no longer energy could be supplied hence decay i.e.
breakdown of tissues take over. So death simply means sessation of
energy input.
Thermodynamics
and Society
2.7. It may sound a bit queer but if we are prepared to think without bias
we shall easily understand how a society's condition can be explained
thermodynamically. Let us take two simple examples. To keep a road neat
and clean the trees by its side must be pruned in time, roads must be
swept regularly, sewerage lines must be kept free etc. All these require
constant input of energy. Now if the persons who are entrusted with these
tasks do not work enough i.e. not enough energy input is made in time for
these tasks, gradually the roads will become dirty and dirtier, trees will
become too big and sewerage will become choked etc. Soon in the
monsoons water logging of the roads will take place and many other
calamities will follow. Then everybody will raise hue and cry and finally
seek monetary help from other countries. people are generally shy to
admit that all these sufferings are due one simple preventable mistake—‘a
stitch in time’—maintainance of the roads in time. Thermodynamically this
means not putting in enough energy in time to maintain order. Hence
disorder takes over.
2.8. Same is true with the education system of many third world countries.
For instance the poor state of education in many places of India to day, be
it in schools, be it in colleges, or be it universities everywhere the energy
input is far less than required for maintenance of order and relevence.
There are instance where the syllabi and the methodologies of teaching
and evaluation are standing still for more than quarter century. The
inevitables are happening.
Enough of these social problems. Let us now move on to ecology.
Passage of Solar
Energy through
Ecosystem
2.9. In all ecosystems the Primary Producers or green plants trap solar
energy into their bodies in the forms of roots, trunks, branches, leaves and
fruits. These trapped energies are used by various secondary producers i.e.
herbivores such as deers, cows, rabbits etc. to form in turn their bodies.
The Tertiary Producers i.e., carnivores, such as tigers, cheetahs, hawks
etc. consume the secondary producers to form in turn, their bodies.
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2.10. Thus solar energy first trapped by Primary Producers (green plants)
is passed on successively through Secondary Producers (herbivores),
Tertiary Producers (carnivores) and so on until all the trapped energy is
completely used up.
2.11. This transfer of solar energy from plants to animals however, is
always partial (cf. 2nd Law of Thermodynamics), the unused energy being
lost to atmosphere as heat. As a matter of fact in all such cases of
transfers of energy from one form into another (here from plants to
animals) are always accompanied with some loss of energy in the form of
heat (cf. as above). This is shown in figure (IV. 2).
2.12. This progressive attrition of energy captured by plants, during its
passage from plants through others such as herbivores, carnivores etc. till
the energy is completely dissipitated, has led to the emergence of a very
useful concept known as Pyramid of Life (or Ecological Pyramid) shown
in Fig. IV 3. This concept of pyramid of life is graphically presented in a
sequential order in which energy is passed on through all categories of
living beings of any ecosystem. Such graphical presentations may use
either energy or mass or number as parameter. Let us take as an
example—the Indian forest of Nilgiri Mountains in State of Chennai. Here
grasses, creepers and trees are the primary producers ; the deers,
elephants, monkeys, birds and insects etc. are the secondary producers ;
and the tigers, wolves, wild dogs and snakes etc. are the tertiary
producers. If we draw three ecological pyramids of this forest using the
above three parameters, the shapes of the pyramids will vary according to
the parameter used and the nature of the ecosystem (Fig. IV. 3a, b and c).
Ecological Pyramid
III. Carnivores
II. Herbivores
I. Producers
III
II
II
I
I
(a) Pyramid of biomass
III
III
II
I
(b) Pyramid of energy
(c) Pyramid of
number
Figure IV.3 a, b, and c Ecological pyramids or pyramids of life.
2.13. Normally one may expect that an ecological pyramid will have the
shape of an usual pyramid i.e., a tetragonal cone with a wide base like
“Pyramids of Egypt”. But this is not always so. The shape of the pyramid
i.e. Pyramid of Life depends upon both the parameter and also the nature
of the ecosystem (as mentioned earlier). For instance, if the parameter is
number but he ecosystems are different—one a forest and another a
grassland, their pyramids would be somewhat like this (Fig. IV. a and b).
Parameters and the
shape of the
Pyramids
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Ecology for Millions
(a)
(b)
III
II
I
Figure IV.4 a & b Pyramids of number of two different ecosystems
(a) Grassland (African savannah) (b) Forest (Congo river basin).
2.14. In both the figures the stages I, II and III are arranged on the basis
of their numbers. In (a) i.e. grassland the number of grasses are far
more numerous than the herbivores—mainly antelopes, deers and
wildebeests but in (b) i.e. forests the number of trees and shrubs are less
than the total number of herbivores which include birds and host of
insects etc. So here we get an odd-shaped pyramid with base being
narrow, middle wide and top narrow again. Now, if we take biomass as
parameter, the shape of the pyramid for same ecosystems may not always
be cone-shaped. With energy as parameter however, the shape of the
pyramid irrespective of the nature of the ecosystem, will always be
conical as, the energy utilised by any step will always be less than energy
utilised by the preceeding step. This is a very important law of Nature
which can be used to solve our chronic food shortage.
2.15. Summing up, the solar energy which autotrophs trap, become
progressively dissipated as it passes through the successive stages of
heterotrophs in an ecosystem. We shall come to ecological pyramids once
again later in this chapter.
3. LIGHT AND PHOTOSYNTHESIS
3.1. Solar radiation which is vital for photosysthesis consists of a range
of electromagnetic waves whose wavelengths vary from very short and
high energy gamma rays (10–10 cm) to very long radiowaves (10 4 cm).
But most of it which is lethal to protoplasm is screened off in the Earth’s
upper atmosphere. Only the visible lights (±10–4 cm) and a little of ultra
violet, a little of infra red and a good deal of radio-waves reach the
surface of earth.
3.2. The white sunlight that we see is formed by blending seven distinct
colours ranging from 400 to 750 µm. Each colour of sunlight is
characterised by light of a distinct wave length. If we pass a beam of
sunlight through a prism (triangular shaped optical glass), the sunlight will
break up into its original seven colours and we shall get what physicists
simply call a solar spectrum (Fig. IV. 5.).
3.3. This spectrum of sunlight has seven colours. These are, from one end,
violet, indigo, blue, green, yellow, orange and red. In short this is named
‘VIBGYOR’. Beyond violet there is ultra-violet (U.V.), and beyond red there
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U.V. (Utra violet)
not visible
Violet
Indigo
Blue
Beam
of
sunlight
Visible
range
(VIBGYOR)
Green
Yellow
PRISM
(which splits the
sunlight into its
component colours
i.e. wavelengths)
Orange
Red
I.R. (Infra red)
not visible
Figure IV.5 Solar spectrum i.e. spectrum of sunlight,
reaching Earth’s surface and visible to us.
600
Infrared
Orange
500
Red
Green
400
Blue
Violet
Relative absorbance
is infra-red (I.R.) both of which are invisible to us. The colour of the light
will depend upon the wavelength of the light. For photosynthesis the green
plants use only a portion of the visible spectrum (given before) i.e. some
colours only and not all (Fig. IV. 6). This figure should be seen along with
the previous figure i.e. solar spectrum (Fig. IV. 5).
700
Wavelength (mm)
Figure IV.6 Absorption spectrum of chlorophyll a.
3.4. It is quite obvious from the above absorption spectrum that blue and
red are the two colours whose relative absorbance for photosynthesis by
chlorophyll are highest. Green is least absorbed hence forest are green.
There are however other pigments such as carotenoids which use green
colour for photosynthesis. Sea water does not absorb the blue colour. So
sea is blue.
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How much sunlight is
used in Photosynthesis and what the rest
do?
Ecology for Millions
3.5. Leaves etc. i.e. phosynthetic areas of plants absorb only 50% of the
sunlght that impinges on them. Of this only about 2% is utilised in
synthesising biomaterials. This means that the gross efficiency in
producing biomaterials by plants by using energy of sunlight is only 1%.
The remaining 99% of solar energy which is not used up in
photosynthesis, is however, not wasted but indirectly keeps the planet
alive. Some uses may be given here. Solar energy heats up sea surface
causing water to evaporate leading to formation of clouds. Air currents
again created by air warmed up by sunlight, carry these clouds all over
the earth causing rainfall and snows. Snows in turn feed the rivers and so
on. So besides photosynthesis, causing rainfall, wind current and snows
are some of the most important life-saving roles of sunlight.
3.6. There are many more such uses which need not be elaborated here.
Suffice it to say that sunlight is not only responsible for photosynthesis
and rainfall but also the entire weather system of Earth and many other
roles. Recently it has been shown mathematically by Edward Lorenze that
a very small change in the weather in one corner of Earth may lead to a
big change in weather elsewhere (Butterfly Effect or Chaos Theory,
1972). Sunlight is really life to us. Later in the chapter on POLLUTION
more on this will come.
3.7. The intensity of sunlight depends upon its nearness to tropics. The
further a place is from tropics the lower is the intensity of sunlight. Also,
in the same ecosystem a plant that grows under a tree will receive less
sunlight than the top of the tree (i.e. canopy) which gets sunlight directly.
From this angle of light and shade, a forest has at least two storyes, —
Canopy i.e. the tree tops which is fully exposed to sun and Understorey
i.e. the area under canopy which does not get much of direct sunlight
(Fig. IV. 7.).
EMERGENT (above
canopy occasional trees)
CANOPY
UNDERSTORY
GROUND
Figure IV.7 Forest with canopy and understorey.
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3.8. Thus plants belonging to the same ecosystem become differentially
adapted for photosynthesis according to the intensity of sunlight at their
exact locations. So some plants become shade adapted while others
become light adapted.
4. ENERGY CIRCUITS
4.1. The energy synthesised and stored by autotrophs (i.e. green plants)
during photosynthesis, gradually passes through various heterotrophs (i.e.
herbivores and carnivores) i.e. secondary and tertiary producers and so on
till the entire quantity of solar energy trapped by the plants is released
back into the environment. This particular pathway of stored energy
through an ecosystem is called Energy Circuit or Energy Pathway
(Fig. IV 8.).
ECOSYSTEM
g
su
nl
ig
Bacteria
ht
HEAT
SINK
In
co o r g a
m
po n i c
ne
nt
s
in
g
m
Outgoin
co
not
Sunlight
plants
used by
In
Return to
ecosystem thru
bacterial action
Figure IV.8 A schematic diagram of energy-circuit and material circuit in an ecosystem.
(P1, P2, P3 and P4 are the producer1 i.e. green plants, producer2 i.e. herbivares,
P3-carnivares and P4 i.e. the top carnivares such as parasites etc.).
4.2. From the above figure it will be apparent that food materials
synthesized by green plants (P1) pass from them to the herbivores (P2)
and from these to the carnivores (P3) and finally to top carnivores (P4)
such as lions and tigers on land and sharks in sea and parasites. Such
Grazing Circuit and
Detritus Circuit
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passage of energy through stages P1 to P4, through successive states of
eating and being eaten is known as Grazing Circuit. When energy,
instead of passing through successive stages of grazers, pass mostly
through bacterial actions on dead and decaying bodies, then such an
energy circuit is known as Detritus Circuit. Such circuits occur in sea
beds or beds of deep lakes where the beds become muddy owing
primarily to accumulation of dead and decaying organic bodies. Dead
bodies of plants and animals constantly fall like shower upon the bottom
dark surface of sea-bed from the top sunlit surface of the sea, to be
broken down by bacterial action.
4.3. Other features of ecosystem apparent from the figure (IV. 8) are as
follows :
3.(1) Only a part of the biomaterial produced by one producer is
available to the next producer. Rest of it is directly used up by the
producer itself for its own various metabolic needs and decomposition
after death by bacterial action. As a result most of the biomaterials
produced are quickly broken down and returned to the abiotic component
of the ecosystem to be recycled again.
3.(2) The energy component of each stage i.e. P1, P2 etc. is partly
passed on into the ecosystem through their successive stages—(just like
biomaterials) but rest of it is directly released into the ecosystem without
the intervention of the bacteria (Fig. IV. 8). Still there is a difference
between the two. Unlike biomaterials which are recycled again and again
the energy however once released into the ecosystem cannot be recycled.
It is lost irrevocably. This method of loss of energy from ecosystem is
called passage into heat sink just as water poured into a kitchen sink is
no longer available. This important difference in the behaviour of energy
and mater is to be remembered.
Role of Sun and
Clairvoyance of
ancient sages
4.4. Our Sun is the constant and unending source of energy which is
keeping our ecosystem going on and thus the ultimate provider of all our
requirements. Thus food, fuel, household items, fire, weather, ocean
current, rains and other glorious and beautiful features of our Mother
Earth all of which have come through solar energy, have made Earth a
unique planet in our Solar System. Ancient sages rightly guessed the
importance of Sun in our lives. Here lies the root cause why Egyptians
worshipped Sun as a most benevolent god—Ra. Persians too worshipped
Sun as their principal god (Chap. I) and Hindus worshipped Sun as Sun
God or Surya Devata. These examples tell us of the excellent power of
observation and understanding of our forefathers about the important roles
of Sun and Nature in our lives. [Please see the poem in the beginning of
this chapter (IV)].
4.5. If we measure the amounts of energy fixed by one producer against
another, preceeding or succeeding, according to a descending order i.e.
parent producers occupying the lower rungs and the consumers the
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77
upper, we shall get an usual conical structure i.e a conical tetrahedron—
the pyramid of energy. This means the base would be widest with the
upper tiers successively narrower (Fig. IV. 3). While the pyramids of
energy of any ecosystem will always look normal i.e. base wide and the
tip narrow, but other types of ecological pyramids of the same ecosystem
such as, pyramid of biomass and pyramid of number may not always
look so (Fig. IV. 9).
Ecological Pyramids
(a follow up from
IV.2.11)
P3
P
P2
P2
P1
(a) P. of energy
P1
(b) P. of biomass
(c) P. of number
Figure IV.9 Ecological pyramids of the same ecosystem–i.e. a tropical rainforest
but using three different parameters—a. energy, b. biomass and c. number.
4.6. In this ecosystem (tropical rainforest) P1 are trees, P2 are insects and
P3 are birds. While the pyramid of energy (a) for any ecosystem will
look normal i.e. like a conical tetrahedron but the pyramids of biomass (b)
or number (c) however may not look normal for all ecosystems. For
example here the ecosystem being a forest the P 1 are trees, P 2 are
insects (mostly) P3 are birds mainly. So here necessarily the pyramid of
number (c) is an inverted one. In another type of ecosystem say, the
Afrikan savanna the P1 mainly consists of grasses and a few trees, P 2 of
deers, wildebeests and zebras and P3 of Lions, Cheetshs and Hyenas. Here
the Pyramids (a), (b) and (c) all look normal i.e. will have a normal
pyramidal shape (conical tetrahedron). Therefore it should be remembered
that for a comparative study of one ecosystem with another, the pyramids
of energy are most reliable.
5. STANDING CROP, CARRYING CAPACITY AND
PRODUCTIVITY
5.1. In shallow ponds for artificial fish culture, we shall have only 2 or 3
varieties of producers. The P1 would mostly constitute of phytoplanktons
and P2 mostly of small fishes and some zooplanktons. Here if we weigh
P1 and P2 separately, we shall find P2 far outweigh P1. Although it may
seem odd to see how so small amount will of P1 can support so large
amount of P2, the following consideration will help to understand. The
time required to mature and duplicate for a species may vary from species
to species. A phytoplankton may require less than a day to duplicate itself
but a fish may require more than a year to mature and breed. In this case
the fishes might have grown for months to acquire their weights but the
phytoplankton in the same pond might have multiplied more than hundred
times within the same period. That is how apparently small amount, by
Standing Crop
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Ecology for Millions
weight, of P 1 can support or carry an apparently large amount, by
weight, of P2.
5.2. This also helps us to understand the concept of Standing Crop. The
Standing Crop is a measure (by weight, volume or else) of any particular
species or any group of species in a particular ecosystem at a particular
point of time. This is a very helpful concept. This gives us a quantitative
assessment of a particular type of biomaterial (ex. crop, fish, food grains,
cubic feet of wood or Kg. of beef etc.) that is available as standing crop,
for harvesting or some other need in a particular ecosystem at a particular
point of time. A forestryman may talk of how many cubic feet of
commercial wood per acre a particular forest may give or, an animal
husbandry man may talk about how many kg. of beef per acre a pasture
can yield at a particular time.
Carrying Capacity
5.3. The Carrying Capacity of an ecosystem means the capacity of one
level of producers to support the growth and survival on a more or less
permanent basis of another, higher group or producers. Here is an
example from pond ecosystem. The standing crop of only a small amount
of phytoplankton can support a much larger quantity of fish population
(explained earlier). Hence this is the carrying capacity of the
phytoplankton of this pond for this fish population. Naturally the nature of
both the groups of species (P1 and P2 or P3) i.e. the species supporting
and the species supported will determine the carrying capacities of an
habitat or an ecosystem for the species one is interested in. The nearer a
species is to the autotrophs, the more will be the carrying capacity of that
habitat for that species. Here is an example from Kendeigh (p. 167). A
density of 100 deers is required to support one wolf (after Pimlett 1967).
Perhaps one thousand acres would be needed to feed 100 deer. In this
way one can estimate how much land would be required to support one
community of deers (of P2) or wolf (of P3). We shall descuss more on
this theme later in chapter on POPULATION.
6. PERCENTAGE OF SOLAR ENERGY USED AND WORLD PRODUCTIVITIES
Only 2% of sunlight
utilised by autotrophs
6.1. Before concluding this chapter it would be interesting to examine how
much solar energy is really used by autotrophs. Average solar energy
impinging upon per square metere of land is about 200 calories per day
(world average) and autotrophs absorb only 2% of usable light energy of
which only half (i.e. 1% of impinging light energy) is utilised in
photosynthesis. This is the world average. The entire bioproductivity of
the world comes only from this 2% of solar radiation absorbed by plants.
With this mere 2% of solar radiation absorbed, the primary producers of
the world (P1) manufacture 170 billion tons of biomaterials annually.
This includes the entire biosphere i.e. lakes, forests, deserts, seas and so
on. The productivity of all places are naturally not same. It varies from
one ecosystem to another depending upon the presence or absence and
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79
quantity and nature of +ve and –ve factors for production. For example,
presence of adequate nutrients is a positive factor. Ample sunlight is a
positive factor. Reasonable amount of wind current or water current are
positive factors as currents help the supply of oxygen and remove
unwanted metabolic products. Also up to a point, temperature is helpful
for growth. On the other hand too much of heat or, too much or cold or
too high winds all are negative factors for productivity.
6.2. Agriculture is essentially creation of an artificial ecosystem where,
for certain selected species such as, rice, wheat , maize or cows, sheep
and poultry etc. the specific positive factors for productivity are boosted
such as, fodder and minerals for cows, sheep etc. and nutrients and water
for crops and also the elimination of competitive species such as weeds,
pests etc. in order to ensure a very high productivity of grains or standing
crop as the case may be, from the point of view of the requirements of
humanity. Still it would be well-worth to remind ourselves of the fact that
the world average of utilisation of solar energy for primary production
(P1) is only 2%.
6.3. A look at the following table (Table IV. 1.) will give us an idea about
the net annual primary productivities and biomass of all major
ecosystems of the world. This compilation by R. H. Whittaker (1975) is
a very useful one. For example it can help planners to focus on such
ecosystems where investments to augment primary production to yield
maximum output vis a vis capital invested. It would also help to do the
opposite i.e. help to decide for which ecosystems paying attention may
wait. Also it should be noted that the net annual world primary production
is 170 billion tons from which all our and the requirements of other
consumers such as fishes, deers, tigers, elephants, birds etc. etc. are
met. And all this 170 billion tons come from only 1% of solar energy that
reaches the ecosystem. Rest 99% of solar energy absorbed by plants
goes for other things such as weather regulation, creating ocean currents,
rains etc. all of which collectively keep the biosphere alive.
6.4. It seems it would be an interesting mathematical speculation to work
out a computer model and estimate what would be the likely fall-out if,
say, through genetically enginered plants we succeed to utilise instead of
present 1%, 1.25% or even 1.5% of solar energy that reaches the earth
surface. Would the meteorological ripple that would result may, through
butterfly effect (Chaos Theory), bring havoc in our earth through
changes in weather? Would this lead to serious tampering with Nature?
Off course tampering with Nature in small ways have already started
long ago. When we became herdsmen instead of food gathers (Paleolithic
Age) we tampered with ecosystem. Again when we became agriculturists
instead of herdsmen (Mesolithic Age) we once again tampered with
Nature. Electricity, damming of rivers, deforestation, atom bombs, genetic
engineering etc. all are forms of tampering with Nature’s Ways. Some of
Ecological basis of
Agriculture
Certain observations
on this Table on
World Net
Productivity
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80
Ecology for Millions
Table IV.1
NET ANNUAL PRIMARY PRODUCTIVITIES AND STANDING
CROP BIOMASSES OF VARIOUS ECOSYSTEMS OF THE WORLD.
(After Whittaker, 1975; from Begon, Harper and Townsend, 1990. p. 652)
Ecosystems
Area covered
(106 Km)2
Net primary productivity per unit area
Biomass (standing crop)
Mean
Productivity
gm/m2/area
World Net
Production
(109 ton)
17.0
7.5
5.0
7.0
12.0
8.5
15.0
9.0
8.0
18.0
2200
1600
1300
1200
800
700
900
600
140
90
37.4
12.0
6.5
8.4
9.6
6.0
13.5
5.4
1.1
1.6
45
35
35
30
20
6
4
1.6
0.6
0.7
765
260
175
210
240
50
60
14
5
13
24.0
14.0
2.0
2.0
3
650
2000
250
0.07
9.1
4.0
0.5
0.02
1
15
0.02
0.5
14
30
0.05
Total Continental
149.0
773
115
12.3
1837
Open ocean
Upwelling zones
Continental shelf
Algal beds and reefs
Estuaries
332.0
0.4
26.6
0.6
1.4
125
500
360
2500
1500
41.5
0.2
9.6
1.6
2.1
0.003
0.02
0.01
2
1
1.0
0.008
0.27
1.2
1.4
TOTAL–MARINE
361
152
55.5
0.01
3.9
TOTAL–WORLD
510
333
170
3.6
1841
Tropical rain forest
Tropical seasonal forest
Temperate evergreen forest
Temperate deciduous forest
Boreal forest
Woodland and schrubland
Savanna
Temperate grassland
Tundra and alpuse
Desert and semi-desert schrub
Extreme desert, rock, sand
and ice
Cultivated land
Swamp and marsh
Lake and stream
Per unit
area wva
(Kg m–2)
World
biomass
(109 ton)
the consequences are already making us worry. It is time planners pay
more attention to ecological consequences before initiating large scale
manipulations with Nature.
6.5. Finally, it may be worthwhile to consider as below. God has created
all of us—men, women, animals, plants, birds, fishes, insects, earthworms
and all. ALL are God’s children and hence ALL have a right on this
Garden of Eden—Mother Earth. We have now admitted women’s right; is
it not time we also admit rights of plants and animals for a safe corner in
this “Garden of Eden”? The present day Nature Parks are too small.
What makes men think that we are the undisputed owners of this Earth?
Never before the Earth has been violated so much through plundering of
her resources and ravaging her body by the ever growing lust of
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Bioenergetics
81
populations of Homo sapiens, as it is being done today. It is time we tarry
a while and ponder about the rights and requirements of the other citizens
of Earth—plants and animals. It is time enough we concede their right to
live and allow them the citizenship of this planet. Hindu sages perhaps
meant this when they announced
‘All are Manifestations of God’
— translation - author’s
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Chapter V
Bio-Geo Cycles of Chemicals
(The Eternal Cycle)
Topics
V.1. The Principle
V.2. Various Types of Cycles
V.3. Various Aspects Related to Bio-Geo Cycles of Chemicals
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85
CHAPTER V
BIO-GEO CYCLES OF CHEMICALS
(The Eaternal Cycle)
“I was, I am and I shall be”
— Geeta.
(A part of Krishna’s advice to Arjuna described in the epic Mahabharata)
1. THE PRINCIPLE
1.1. In the preeceding chapter we have seen that energy passes through
the ecosystem in a constantly diminishing manner until it is irrevocably
lost into the environment. Thus in ecosystem energy does not recycle but
flows on.
1.2. Here we shall see it is not so with materials. Materials in ecosystem,
do not get lost but recycle again and again. Materials locked up in living
bodies return to the abiotic environment after the death of the living
beings. These materials are again picked up by plants to produce new
biomaterials. This cyclic passage of inorganic materials from the abiotic
environment into the biotic bodies and return from these to the abiotic
environment again is known as Bio-Geo Cycle of Chemicals. This
process is repeated again and again in nature as an unending cycle.
1.3. In the end of this chapter we shall see how clairvoiantly the author of
the Vedic scripture “GEETA” (sage Veda Vyas) perceived the essence of
the ‘bio-geo cycle of chemicals’ and put it so effectively in so few words
which is given in the verse in the beginning of this chapter. We shall
come to this verse or ‘Sloka’ again in the end of this chapter.
1.4. Besides solar energy which is a must, plants also require certain
specific chemical elements in order to synthesise biomolecules. These
elements are specific and many of them are abundant in Nature, but not
all. These elements are needed in varying proportions by all plants and
animals while some elements particularly sodium is needed by animals
only but scarcely by plants. Following is a table listing these elements and
showing their relative amounts in the bodies of plants (maize) and animals
(man) (Table V. 1).
The Chemical
Elements Living
beings Require
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Ecology for Millions
Table V.1.
MOST CHEMICAL ELEMENTS REQUIRED BY PLANTS
AND ANIMALS, (%) OF DRY WEIGHT.
(From Ecology – ed. by Moore – 1986, p. 12)
Elements
Plants (Maize)
Animals (Man)
44.4
43.6
6.2
1.5
1.2
0.9
0.2
0.2
0.2
0.2
0.1
0.1
0.1
0.04
–
–
–
98.94
14.6
56.0
7.5
9.3]
0.005
1.1
4.7
3.1
0.2
0.8
0.5
–
0.01
–
0.5
0.01
0.005
98.33
Oxygen
Carbon
Hydrogen
Nitrogen
Silica
Potassium
Calcium
Phosphorus
Magnesium
Sulfur
Chlorine
Aluminium
Iron
Manganese
Sodium
Zinc
Rubidium
Total
(Here three points are worth mentioning. The totals of neither maize
nor man adds up to100% implying that there are other elements which
may be required in trace amounts. For example, some animals need
vanadium. Secondly, the proportion of the main elements substantially
vary between plants (e.g. maize) and animals (e.g. man). For example,
maize require 44% of oxygen but man only 14.0%. Thirdly, certain
elements such as sodium are needed by animals and not by plants.
Sodium is crucial for nerve transmission hence animals must have it. As
sodium is scarely present in many plants many forest animals and birds
must specially supplement sodium in their food by licking sodium-rich
soils. Forest Rangers sometimes specially provide sodium salt for animals
to come and lick when needed).
2. VARIOUS TYPES OF CYCLES
2.1. Movement of each element, (such as, Carbon, Hydrogen, Iron,
Phosphorus, Calcium etc. etc.) within living bodies has a specific cycle
of its own. Each cycle is characterised by various steps. One part of this
cycle is spent within living bodies as constituent of biomolecules and the
other part in the abiotic environment as inorganic molecules.
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Bio-Geo Cycles of Chemicals
2.2. In Nature some elements stay, in a gaseous state. For example,
Nitrogen (N) before being picked up by plants, i.e. outside living bodies
stays in the form of gas—a constituent of air. Other elements such as
Phosphorus (P) and Sulphur (S) when outside the living bodies stay in
solid state as phosphates and sulfides respectfully. There are still another
group of materials such as water and carbon dioxide (H 2O and CO2)
which pass through both a gaseous and a solid state when these stay as
non-living components of the environment. So these have a dual state i.e.
a combination of gaseous and solid state. Outside living bodies water
stays both as gas (water vapour in air) and as liquid (water in soil, rivers
and lakes) or as solid as ice in polar caps and mountain tops) while
carbon dioxide stays either as gas (in air) or as solid (as carbonates).
87
Three types of BioGeo Chemical
Cycles
2.3. So we have generally three types of Bio-geo Cycles of Chemicals.
(a) Gaseous cycle e.g. nitrogen.
(b) Sedimentary cycle e.g. Phosphorus and sulphur,
and (c) Dual cycle e.g. water and carbon dioxide.
Let us examine one example of each of these three types of cycles.
2.3.(a) A Gaseous Cycle
(i) Nitrogen is an essential component of protein molecules. When
living beings die and their bodies get decomposed by bacteria, nitrogen is
converted, through stages, into nitrate salts and later released into the
atmosphere as the gas NO2. The NO2 component in the atmosphere is the
main nitrogen storehouse of earth. This gaseous nitrogen through various
agencies becomes reconverted into nitrate salts or ammonium ions which
green plants (autotrophs) pick up to synthesise biomolecules.
The Nitrogen Cycle
(ii) This cyclic passage of nitrogen from living beings to soil and
water to atomsphere and return from atmosphere again through soil and
water, into the the bodies of living beings is called THE NITROGEN
CYCLE (Fig. V.1). As when outside living bodies, nitrogen stays in the
atmosphere in the form of gas the nitrogen cycle is called gaseous cycle.
2.3.(b) A Sedimentary Cycle
(i) Phosphorus is another essential element of living beings. Molecule
of DNA, RNA and ATP must have it. After decomposition following
death, phosphorus compounds enter the soil and become phosphate salts
and stay there till these are picked up again by autotrophs (green plants)
so that the cycle may restart. Plants use phosphorus as orthophosphate
ions (H2PO4–). If however plants can’t pick up phosphorus soon enough,
it runs down along with rainwater and gets sedimented into sea-beds from
where its return to biocycle is very slow. There is however a phenomenon
in sea called upwelling (for explanation see later in this chapter) through
which part of this phosphorus, which has found its way into sea beds,
returns again to land and thence into the bio-geo cycle.
The Phosphorus
Cycle
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Ecology for Millions
Nitrogen in
biomaterials
(Plants & Animals)
Aft
er
de
a
th
gh
throu
tion
osi
mp
n
co
ctio
d e i al a
r
cte
o
nts
y pla
is b
s
e
nth
sy
n
i
te
itr
inngg
mi
rm
ffoar
n
sy
tein
Pro
Pr
of
n
trogen
of n i
htening
g lig
Nitrate salts
in
soil & water
Fur
t
h
e
r ba
cte
r
i
a
sa l
la
ts
ct
io
og n
e
ing
en
trog
f ni
e
g o som
xin gh ria
Fi hrou bacte
t ooiill
sr
ge
ro
nit eria
t
of
ac
a se
Rele ugh b
o
il thr
om
frso
n
l a fro
ct i m
on
s
rin
du
Fix
by green p
lant
nthesis
s
ba
Ammonia
Nitrogen pool in
atmosphere
Figure V.1 The nitrogen cycle.
(ii) When plants and plant products such as, wood, coal and
petroleum (the latter two are only fossilised wood), are burnt as fuel,
phosphorus goes into atmosphere as gaseous compounds. With rain this
phosphorus comes down to soil and become phsophates again. When
plants do not pick up all phosphates from soil soon enough, gradually the
unutilised phosphorus moves along with soil-water into the river and
thence into the sea. From sea only a small portion of phsophorus is
brought back to land through food-chain (vide infra). A large portion of
phosphorus in sea however settles down as sediments in deeper water
whence its return is extremely slow and little at a time.
(iii) Phosphorus recovery from sea-water through food-chain is
effected in the following way. Both phytoplankton and zooplankton pick
up phosphorus very quickly from sea-water. From planktons this soon
finds its way into the sea fishes who live on planktons. From fishes
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Bio-Geo Cycles of Chemicals
89
phosphorus is brought back to land through two pathways. One via
trawlers who harvest sea fishes extensively for our dinner table. The other
route is via sea birds. Sea birds who spend the day in sea catching and
eating fishes, return to coast in the evenings to roost for the night. Their
droppings are extremely rich in phosphorus. So this is the other route for
return of phosphorus to land (Fig. V. 2.).
From
land
To s
h
To de
allow
eper
er
te-1 s)
Rou h fishe
-2
g
Route a birds)
ou
e
s
(thr
h
g
(throu
wate
r
wate
r
Phosphorus retrieval
from Sea through
Food Chain
To
land
Planktons
Sea
Sediments
Figure V.2 Phosphorus retrieval from sea.
(iv) Here we would like to mention an interesting thing. Generally
bird droppings are rich in plant nutrients. Chicken droppings, pegion
droppings, even bat droppings, are used by farmers in Sumatra as plant
manure. Excrements from sea-birds are even more so as these are formed
from extremely phosphate rich food—fishes, which these birds live upon.
Sea birds have a habit of roosting at nights in the same spot throughout
their lives and this goes on for generations—hundreds of years—forming
mountainous heaps—several metres thick layer of an extremely phosphate
rich material commercially known as GUANO. In the western coast of
Chilli there is so extensive stock of Guano that the country has been
exporting Guano as fertiliser and earning good revenue.
(v) Similarly there are some small unihabited islands West of Africa
which are used by sea birds for roosting at nights. Over the years these
islands too have become so rich in Guano deposits that some people from
mainland Afrika make their living by collecting and selling this harvest of
Guano—a bird product. There is a novel “Bridge of the Magpies”
(Geoffrey Jenkins 1975) depicting the activities of some questionable
characters in such uninhabited, Guano rich West Afrikan islands.
(vi) Ocean beds are not always flat. In some places there are
mountains running North to South. Recently National Geographic Society
(of Washington D.C., U.S.A.) has published very good maps of ocean
floors. There are some such elevations west of South America and West
Guano
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Ecology for Millions
of Africa. When the ocean currents moving from West to East strikes
such submerged mountains the cold deep sea currents move upwards
carrying phosphate rich sediments along with them. This physical process
of cold deep sea water welling-up is known as UPWELLING (Fig. V. 3.)
In seas such zones where upwelling takes place are very rich with
phosphates and hence abounds with planktons and hence fishes which
feed on these. Such areas of are full of sea birds and now-a-days with
fish trawlers as well. In this way, formation of guano deposits, are direct
consequences of sea birds droppings on land.
Upwelling and
retrieval of
phosphates
ZONE OF UPWELLING
Sea Birds
SEA
SEA
SEA BED
SEA BED
Figure V.3 Upwelling.
Pegion droppingsa free source of
manure
(vii) Thus phosphates return to land from sea by two pathways. First,
through sea-fishes harvested from sea by trawlers and fishermen using
small boats. Second, through guano deposits formed by droppings of birds
who live on sea fishes mostly from upwelling zones of sea. The entire
phosphorus cycle is being summarised in the following figure (Fig. V.4.). As
outside, living bodies, Phosphorus stays in land in the form of solid
phosphate salts, the phosphorus cycle is called a semimentary cycle.
(viii) In this connection it occurs to us that keeping a few pegions,
by towns people who maintain kitchen garden or potted flowers in their
houses would provide them a free source of garden manure. This would
be both an environment-friendly as well as handy source of manure.
2.3.(c) A dual Cycle
(i) Water is a mojor content of the bodies of living beings Water
contents ranges from 50% or so in hardwoods to 95% or more in jelly
fishes. Without water life would not be possible.
The Water Cycle
(ii) Most of the water content of earth is in huge reservoirs like seas,
lakes, polar ice and underground. Water in transit is in the form of clouds,
rainwater and rivers. This is not much in quantity and the water locked up
a biological systems is ludicrously tiny. However one must hurry to add
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Bio-Geo Cycles of Chemicals
ion
sit
o
)
p
m tion
c
Rain
ATMOSPHERE
Ra
u
fis ppe
he
r
s
in
Re
tur
n
up from
we
llin
ugh
thro
ers
lay
ir d s
er
ab
ep
se
de and
g
fro
n
tu r
ug
Re thro
er
lay
h
Burning of
coal & wood
po
om tio
c
e
c
&d
la
ath cteria
e
D
(ba
SOIL
m
s
n) ition
Phosphoreus
in living beings
PLANTS. ANIMALS
Up
t ak
eo
p la
fp
n ts
(pr hos
p
ot
ei
n
s
De
a th
(ba & d
c te e co
r ia
la
by )
us esis
r
ho nth
y
91
SEA
Figure V.4 Phosphorus cycle.
that in Nature’s designing nothing is ‘ludicrous’—everything is
programmed and relevent. Here is the water-content of the various
sections of biosphere (Table V. 2.). The information given in this table is
a very thought provoking one. We may have to refer to it again at the end
of this book.
(iii) The journey of water from the living to the non-living and back
to living takes the following route. Water comes out from the living
systems through respiration, transpiration, perspiration, metabolism and
decomposition after death. Water from these evaporate, go into the
atmosphere and form part of the cloud formations. In the meantime
simultaneously due to solar radiation, water constantly evaporates from
sea, land, rivers, lakes etc. to form the bulk of the clouds. These cloud
masses are carried along with wind currents and when situation favours
(mainly due to drop of temperature) condense into water droplets and
come down to earth either as rain or snow. Rainwater moistens the earth.
Rain
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Table V.2.
WATER CONTENTS OF VARIOUS SECTIONS OF BIOSPHERE
(After Data of R.L. Nace from Colinvaux)
Sections
Oceans
Glaciers and Polar Ice
Ground Water
Soil Water (part of life)
Freshwater Lakes
Inland seas and Salt Lakes
Rivers and Streams
Atmosphere (clouds and vapours)
Amounts (million cubic kilometer)
% Total
1322.0
29.2
8.4
0.067
0.125
0.104
0.001
0.13
97.21
2.15
0.62
0.005
0.009
0.008
0.001
0.001
From moist soil, plants take in water and other nutrients so that
biosynthesis continues. Not all clouds rain on lands. In fact most clouds
rain on seas, some only on lands and the remaining come down as snows
on mountain tops, polar regions and cold temperate zones. Mountain
snows melt in summer and feed the rivers. Part of the water from snow
percolates into the soil and nourish the ground water. Not all rainwater
that falls on land enters the plants. Most of it however enters the soil to
recharge the ground water system or aquifers and some evaporate to feed
the clouds and the rest feed the rivers. Ultimately all the ground water
flows into seas. Thus gradually with time, all water in the clouds find
their way back into the seas. From sea the cycle starts again (Fig. V. 5.).
(iv) Rainwater on land is the lifeline for vegetation, agriculture, forests
and their animals. All rainwater however do not go into these. A
considerable part of it percolates down into the deeper layers of soil, a
process called leaching carrying down with it the harmful salts like
arsenic etc. Ultimately however all water finds its way into the sea.
Another very important function of rainwater is to recharge the waterbearing strata of the soil—the aquifers.
Deep Tubewells:
Depletion of Ground
Water
(v) When we sink deep tubewells and suck out large quantities of
water for housing projects in towns and intensive agriculture, we deplete
the aquifers more than the normal recharging during the monsoons and
consequently the water table gets lowered. Unless we recharge the
aquifers adequately during monsoon with proper water management, the
groundwater will be further depleted with consequent havocs in various
areas and countries. India is already suffering for neglecting the above
principle.
The duality of
hydrologic cycle
(vi) The duality of the nature of water cycle is owing to the following
reason. The water that is used by the living beings (biota) is the liquid
water which plants take in from soil. Soil gets liquid water from rains and
snows. Rains and snows owe their origin to the clouds which in their
turn are the products of evaporation from sea and land. Therefore
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Bio-Geo Cycles of Chemicals
93
Cloud movement
Mountain
air
Continental shelf
Open ocean
Soil
Water ↓ leached ↓ into the ↓ deeper
layers of soil (aquifers)
Figure V.5 The water cycle.
outside living bodies both the gaseous as well as the liquid stage of
water are musts for an ecosystem. Hence the hydrologic cycle is called a
dual cucle.
2.4. By the above few pages we have tried to explain to our readers the
concept of bio-geo cycle of chemicals with the help of three examples
illustrating three different types. First a gaseous type i.e. the atmosphere
acting as the main storehouse of the nutrient (e.g nitrogen), secondly a
sedimentary type where the soil acts as the main storehouse of the nutrient
(e.g. phosphorus) and thirdly a dual type meaning thereby that here both
atmosphere (and sea) and soil act as the storehouses of the nutrient (e.g.
water).
Summing up
3. VARIOUS ASPECTS RELATED TO BIO-GEO CYCLES OF
CHEMICALS
3.0. Now we shall briefly touch upon a few selected topics on bio-geo
cycles of chemicals a brief information of which might be useful to most
readers.
3.1. Besides its requirements for biosynthesis, water acts as carrier for
nutrients. It is now clearly understood that wanton deforestation and poor
land management causes havoc with nutrient cycling. Here is an example
through phosphorus cycle in Indian grasslands (Fig. V. 6.). The phosphorus
is carried into plant bodies through the root system in the form of
V.3.1. Importance of
water for Nutrient
Cycling
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Ecology for Millions
0.391
Line
shoot
0.126
0.585
Standing
dead
0.267
0.339
Litter
Root
0.629
0.344
0.672
0.748
Soil
39.4
Figure V.6 Phosphorus cycle in Indian grasslands.
orthophosphate ionic salts dissolved in water. Just as haemoglobin carries
oxygen into animal blood stream so does water carries nutrients into plant
sap. Therefore unless adequate liquid water is available in soil near the root
system of plants, this phosphorus cycle is seriously interfered with. As a
matter of fact water acts as the carrier for most inorganic nutrients to
plants. Hence water is a must for survival of forests.
V.3.2. Moderating
Effects of Forests
on Temperature
V.3.3. Standing
Stock, Turnover
Time and Turnover
Rate
3.2. Forests help to keep the weather relatively moderate. Bormann (1976)
has shown that nearly 42% of solar radiation received by a forest is used
up for powering transpiration of water by plants. And it is only through
transpiration that plants get their nutrients for biosynthesis. If there were
no plant-cover this 42% of solar energy would have gone into heating up
the bare ground. So one can easily perceive how important is vegetation
in moderating the local climate. Deforesters would do well to heed this.
3.3. The amount of bio material of a plant/crop present at a particular time
in a area is called Standing Stock. For instance, one can measure the cubic
feet of wood present in a forest in a particular time. This would be the
standing stock of wood of that forest at that time. Similarly, the kilograms
of fish in a pond at a particular time would be the standing stock of fish in
that period at that time. Now if in a pond the standing stock of fish is 20
kg. per square metre and if the annual growth rate is 1 kg. per square metre
than the turnover time is 20/1 i.e. 20 years and following this, the turnover
rate is 1/20 i.e 5% per year. Therefore simply speaking Turnover Time is
the time required to replace the entire amount of standing stock and the
Turnover Rate is the rate of replacement of standing stock taking place in
relation with the amount of the entire standing stock present at that time.
Hence the the turnover time and the turnover rate are very useful criteria for
assessing any parameter of an ecosystem.
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Bio-Geo Cycles of Chemicals
3.4. After death and decomposition the elements or constituents, which
are locked up in the bodies of plants and animals, all return to their nonliving environments. This simply means everything that is locked up
within the biota return to abiota after their death. From abiota, after some
time-gap, these elements or constituents are again picked up by autotrophs
for biosynthesis and thus these enter the biota once again. This period of
waiting by any element or constituent in the non-living environment
(abiota), before being picked up again by the autotrophs, is called the
Residence Time for that element or constituent. This residence time
varies from element to element or constituent to constituent depending
upon the nature of the element or constituent and also the pathways these
follow during their bio-geo cycles.
3.5. Nowadays by using radio-active substances or tracers the pathway
of movement of an element or a compound, through an ecosystem can
be quite accurately mapped. (This is a big area for studies to Indian
ecologists). Through such methods it is also possible to measure the
residence time and turnover time of any chemical or an element through
an ecosystem. For instance DDT. DDT an important insecticide retains its
toxicity for at least ten years, but its residence time in abiota may not be
more than one year or so. Hence within ten years this—poison may
circulate through an ecosystem several times causing severe damages to
the biota. This is affected in the following way. DDT when sprayed in the
fields to control insect-pests, soon reaches the soil and from there gets
picked up by grass etc. When cows eat grass containing DDT, DDT
enters the cow’s bodies and then finds its way into the milk of the cows.
When human beings drink such milk containing DDT, DDT reaches
human bodies (Table V. 3.). Thus DDT which was used in agricultural
fields to kill insect pests, ultimately finds its way into the human bodies—
i.e. from grass to cows and from cow’s milk to human bodies. This
transit of DDT—a poison for insect pests to human bodies need not take
more than a year while DDT’s toxic properties last for ten years. This is
a startling observation. The earlier governments make use of such
information and put restrictions on use of such chemicals whose toxicity
lasts more than a year, the better it will be for all of us. Soon after this
finding U.S.A. has banned use of DDT.
3.6. Raechel Carson was the first person to point out this dangerous side
effect of use of DDT. Carson in her now famous book “The Silent
Spring” (Houghton Mifflin, Boston, 1962) showed most convincingly as
to how DDT from agricultural fields travelled through the rivers into the
bodies of sea-birds. These sea birds who have DDT into their bodies lay
eggs with very thin shells. Naturally such thin-shelled eggs broke when
the parent birds tried to sit upon these to incubate. Egg fatalities became
so extensive that populations or some sea-birds dropped almost to the
verge of extinction. Thanks to Miss Carson's beautifully written book
95
V.3.4. Residence
Time
V.3.5. Poisoning the
Ecosystem: DDT
V.3.6. Rachael
Carson: DDT and
sea birds
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Table V.3.
MEAN CONCENTRATION OF DDT IN HUMAN BODY FAT IN SOME COUNTRIES
(Abridged from Ehrlich and Ehrlich – 1973. p. 133)
Country
Year
No. of Samples
DDT (ppm)
U.S.A.
U.S.A.
Alaskan Eskimo
Canada
U.K.
Germany
Hungary
Israel
India (Delhi)
1942
1963
1960
1966
1964
1959
1960
1964
1964
10
282
20
27
100
60
50
254
67
0.0
10.3
3.0
3.8
3.3
2.2
12.4
19.2
26.0
with convincing arguments and her tireless campaign against use of DDT,
U.S.A. banned use of DDT in 1972.
The famous bald eagles (Haliacetus leucocephalus) of North America
suffered severely from DDT and their number plummeted to only 400
breeding pairs in the lower 48. But soon after 1972 they made a
remarkable spring back in population. Now they have more than 6000
breeding pairs (N G S, July 2002). This ban was followed by other
developed countries as well. Thereafter populations of other affected seabirds also have risen. But India and other underdeveloped countries are
still using DDT and such long lasting insecticides. It seems consciousness
about the latent hazards of synthetic chemicals used in agriculture and in
households is still inadequate in most developing countries.
V.3.7. Cultural Eutrophication: Oyster
Fishery in Cheasapeake Bay, U.S.A.
3.7. DDT is a poison. One would easily understand that accumulation of
too much of any poison or even nutrient in any ecosystem, anywhere is
harmful. The process that leads to such harm is termed Cultural
Eutrophication. Here is an example. There is a bay known as
Cheasapeake Bay near Washington D.C. which receives water from
Potomac river. The watershed (vide V. 3. 9) of this river has many
cultivations which uses heavy doses of chemical fertilisers. Use of
chemical fertilisers is supposed to be good for agriculture. But residual
fertilisers from the fields however are washed into Potomac river
enriching the waters of Cheasapeake Bay so much that, its native plankton
was soon replaced by an entirely new species of plankton. This lead to
near extinction of the valuable oyster fishery of the Bay. This caused a
terrible loss of income to the local fisherman. So we see how a good
thing such as use of fertiliser for agriculture can lead to a bad thing
elsewhere such as loss of a valuable fishery. Fortunately U.S. Govt. took
vigorous corrective measures to ensure that nutrient rich water do not get
into Potomac river and thus upsets its ecobalance. Now they are hopeful
to be able to restart the valuable oyster fishery of Cheasapeake Bay,
U.S.A. (The Washington Post 1999).
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3.8. Recently a Calcutta daily (Bartaman : 21.02.001) reported that
poisonous effluents from a paper mill at Darshana, Bangladesh, flowed
into the river Mathabhanga there. This river soon split into two tributaries
one of which is the river Churni which mostly flows through India (Nadia
district, West Bengal) and finally joined Ganga. So much of the poison
entered the river Churni that plenty of fishes died and people who bathed
in the river suffered from skin problems.
V.3.8. Direct poisoning of fishes of a
river
3.9. The area of land from which water is drained into a river or
lake (or pond) is the watershed of that river or lake (or pond). For
example, the watershed of the river Ganga is spread from Kashmir to
Bihar and West Bengal covering vast areas of Himalayas and Siwalik
Ranges, parts of the states of Delhi, Rajasthan, Himachal Pradesh, Uttar
Pradesh, Madhya Pradesh, Bihar and West Bengal as well as the
neighbouring state Nepal. This area is equivalent to roughly 1.4 million
square kilometres. (Map. II.2). This is quite a big area with extremely
variagated environments ranging from snow-capped mountains of
Himalayas to hot semi-arid ravines of Chambal and also tropical forest of
Southern Himalayas as well as flat alluvial plains of Uttar Pradesh and
West Bengal. Monsoon water from this vast watershed and also water
from molten snow of Himalayas all move towards Ganga—some directly
and the rest indirectly though forests, agricultural fields and some by
percolation through soil. Still only a part of the monsoon showers reach
the river Ganga, rest either evaporate away from the surfaces of the arid
regions or lost through transpiration from forests and agricultural fields
and the rest percolate down into the soil to replenish the stock of ground
water. All these processes play importance roles in maintaining the health
of the watershed i.e. the ecosystems which forms the Ganga watershed.
V.3.9. Watershed
and its Importance
3.10. Like big rivers such as Ganga, small rivers or even brooks have
their watersheds. So have the lakes or ponds. All have their watersheds
(or catchment areas) and naturally their ecosystems. The quantity of the
water that flows into the rivers, brooks, lakes or ponds is very much
influenced by the conditions of the watershed. When an watershed is
disturbed by human interference such as deforestation, agriculture of
creation of cities, roads etc. one or more of the followings happen.
V.3.10. Recharging
of Aquifers
(a) Deforestation leading to temperature rise of the exposed
area. This is because nearly 42% of the energy of the incident sunlight
on a forest is used by plants to provide energy for transpiration of water.
If plants are removed this unutilised energy heats up the place further.
(b) In a deforested place as there are no trees to use water and stop
its flow, so rainwater quickly runs off to the nearest river or lake causing
several damages to the ecosystem such as—
(i) soil erosion,
(ii) raising of the river beds or filling up of the dams,
(iii) causing more frequent floods,
Ills from
Deforestation
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(iv) loss of nutrients from the top soil impoverishing the soil,
(v) impeding the recharging of the water table leading to summer
draught,
(vi) lowering of the water table,
(vii) arsenic poisoning of the well-waters,
(viii) drying up of the lakes and rivers in summer.
(c) Deforestation causes another type of damage to the ecosystem.
When top soil is washed off carrying with it most of the nutrients, the
waters of rivers and lakes become abnormally rich with nutrients. This
causes explosive growth of phyto-planktons and zooplanktons leading to
depletion of oxygen in water. Consequently soon fishes start dying of
suffocation. Thus excessive nutrients in water have a negative effect (also
see V. 7.).
A word About Town
Ponds
Thus the watershed
which is vital for
pond is gone
Summing Up
3.11. Importance of Watershed in keeping the Lakes and Ponds alive.
Here we would like to seek a few minutes of townspeople to talk about
their ponds. With town population soaring, and land price sky rocking the
estate developers are now eying the town-ponds as easy target areas for
filling up and constructing apartments. Naturally local people—the so
called environmentalists protest. But these protests are mostly, of no avail.
By various unholy combinations of people with vested interests ponds are
filled up and the inevitable apartments spring up.
This surrpetitious land—filling is done mostly in the following way.
first the houses are built-up to the edge of the pond, leaving only 10 to 20
feet of land in the margin mostly as road. The locals however promise to
preserve the pond for the beauty of the locality etc. Soon however the
pond is used as a handy dumping ground of garbage by the locals. Even
the images of most earthen idols worshipped by people are regularly
thrown into this pond. So the bed gradually rises. This two pronged attack
on the pond—first by depriving it of its watershed and secondly by filling
it up with garbage soon kills the pond. Only 50 to 100" of annual rain on
its surface is not adequate to keep a pond alive. Soon the dry bed to the
pond is used by the local boys as playground after which the house
builders take over. There were several beautiful ponds in Kolkata which
are now going through such death-spasms. For example, Lake No. 2 of
Lake Town and the pond behind the office of Geological Survey of India,
Chowringhee, Kolkata). [Photo V.1(a) and (b)] Even the ponds of Kolkata
Maidan do not seem very safe. Uniformed public, apathetic government
and greed of estate developers have formed a unholy trinity which is
gradually throttling Kolkata ponds. Soon the park trees may die off for
lack of water in soil.
3.12. If forest cover of a watershed is adequately maintained then
rainwater gets time to enter the soil and thus recharges the water bearing
strata or aquifers and so replenishs the ground water. Such recharged
aquifers help in the following ways—
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Bio-Geo Cycles of Chemicals
99
(i)
(ii)
(iii)
(iv)
Provide water for the trees in summer.
Keep the waterholes in the forest alive throughout the year.
Keep the village wells free of arsenic poisoning
Encourage leaching i.e. poisonous chemicals in soil to go deeper
down as dissolved solutes in water.
(v) Keep the silt load of river waters low and thus keep the rivers
deep and hence reduce the severity of monsoon flooding.
3.13. Since 1930’s United States of America initiated vigorous steps to
maintain and replenish their own forest resources. Today that country has
more trees than before. Their reserve forests are so well stocked with
herbivores that they regularly cull animals such as deers to maintain health
of the forests.
V.3.13. Forests in
U.S.A. vs. India
In India the position is reverse. Though Forest Research Institute of
India at Dehta Dun was established as early as 1906, the forest cover of
India has only shrunk and shrunk. The relative health of the forests
ecosystems of U.S.A. and India would be evident form the following.
U.S.A. has 30% of her land covered with forests while India has only
23%. Again U.S.A. has only 19% of arable land but India has 56% (both
are from C.I.A. data, 1998).
The magnificient herds of bisons of U.S.A. which neared extinction
through hunters with rifles, are now well protected. Their number is
swelling. The story of the royal Bengal tigers is reverse. Following figure
is revealing (Fig. V. 7.). Obviously the Government of India inspite of her
efforts to stem this alarming decline of tiger population, has scarcely
succeeded. Immediately much more is needed.
1920
40,000
1940
1960
30,000
20,000
10,000
1947
Pre-independence
(of India)
Since-independence
(of India)
Figure V.7 The decline of “Royal Bengal Tigers.”
1980
The Comeback of
Bisons but Decline
of Tigers
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V.3.14. Space requirement of animal
and Importance of
Corridors between
Game Preserves
V.3.15. Carbon
Dioxide and Greenhouse Effect
Ecology for Millions
3.14. One must also remember the land requirement of an animal
depends upon its size as well as food habit. A predator like a tiger needs
vast area but a herbivore can manage with a fraction of it. A single
spotted deer may need only 10-15 acres of land for food but a single
tiger would need at least 10 to 15000 acres of land to provide it with
enough prey animals (Col. Keshri Singh, Jaico Publishing House, 1967)
required to survive and breed. Again although vegetarian nevertheless
owing to their large size elephants too require very large areas to support
them. An adult elephant consumes 3 to 400 pounds of vegetables every
day. That is why small game preserve are unsuitable for tigers and
elephants. Besides large mammals migrate considerable distances from
season to season for either suitable pasture or climate. Migrations of
wildebeests of Africa and reindeers of North Europe are classic examples.
(The annual migration of wildebeests and zebras from Serengeti to Masai
Mara in Tanzania is a spectacular scene covering a distance of 400
kilometres). African elephants too travel long distances. Elephants in the
reserves in Northern bank of river Brahmaputra and tigers of Sunderbans
of Assam and West Bengal respectively regularly tresspass into
neighbouring habitations of men. For these reasons if game preserves or
national parks are to be made very effective, these should have not only
plenty of space but these should be, as far as possible, connected with
neighbouring reserves through corridors. If these can be achieved the
animals would have much better chance of prospering. These corridors
should also facilitate north—south migrations. A north south migration
helps animals to tackle rigours of weather.
3.15. Earth’s atmosphere is a very extraordinary mixture of gases. Besides
water vapour it contains 79% nitrogen, 21% oxygen (nearly) and a mere
0.03% carbon dioxide and traces of other gases. Earth is the only planet
we know of which has free oxygen in its atmosphere. Next remarkable
feature is CO2. Plants get their carbon during photosynthesis in the form
of CO2 from atmosphere. Plants again release CO2 into atmosphere during
respiration and decomposition. So essentially carbon cycle is a simple
gaseous cycle—atmosphere → plants → atmosphere. But the story does
not end here. Atmospheric CO2 absorbs infra-red radiation from ground.
Therefore rise of CO2 level in atmosphere is followed with increase in air
temperature. This is known as Green House Effect. It has now been
shown that since 1955 till 1995, the atmospheric CO2 level has steadily
risen from 315 ppm to 355 ppm with annual peaks and troughs (Fig. V. 8).
This gradual rise of atmospheric carbon dioxide is worrying many. They
think if temperature rises steadily arctic snow will melt, sea level will rise,
vast areas near coastline will go under sea and many other calamities may
follow.
3.16. The above group of people are alarmists. There are however people
who believe otherwise. Before delving into their views let us have a look on
the earth’s pool of carbon and its movement through biosphere (Fig. V. 9.).
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101
CO2 concentration (by volume)
360
350
340
330
320
310
1960
1970
1980
Year
1990
Figure V.8 Rise of Carbon dioxide level in atmosphere.
I. CO2 in atmosphere-1.6 %
CO2
CO2
Rain
III. Hydrosphere-94.3%
CO2
CO2 in hydrosphere
several atmosphere
CO
CO22 In
In ‘ooze’
‘oore’
dead
dead faraminifera
faraminifera
Biota
River
Rain
From
Volcanoes
CO2
II Biosphere-41%
CO2 in water + biota
SEA
Industry
CO2
CO2 In limestone:
40,000 atmosphere
CO2 in land
mainly in biota,
coal &
petroleum:
several
atmosphere
LAND
Figure V.9 Earth’s pool of Carbon dioxide and its movement through biosphere.
As mentioned earlier carbon cycle is a gaseous cycle. Plants absorb
carbon dioxide from atmosphere during photosynthesis and releases it
back into atmosphere during respiration. Most of the atmospheric CO 2
however finally finds its way into sea. Sea surface acts as a huge sink for
atmospheric CO2. Surplus CO2 of sea tends to settle down as limestones
in the sea-bottom. CO2 content of sea water is 50 times of atmosphere and
of limestone 40,000 times! Sea is a huge sink for atmospheric CO2. So
the latter group feels that emissions of CO2 due to industrial activity is
too meagre to offset the role of sea as a CO2 sink and change weather.
V.3.16. We need not
be so alarmed after
all
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Ecology for Millions
The present author inclines to agree with the latter view. The rise of
atmospheric CO2 level is a temporary fluctuation which is very likely
owing to extensive deforestations and draining off of swamps and bogs all
over the world. On this issue Colinvaux says as follows. “This is because
a more massive and suden release of CO2 which might be affected by the
agricultural activities than by burning and mining of coal” (p. 593,
Yr. 1993).
V.3.17. “I was, I am,
I shall be”
3.17. Before closing this chapter let me refer again to the opening ‘sloka’
from the religious book GEETA—“I was, I am and I shall be”. From our
understanding of Bio-Geo Cycles of Chemicals we can now easily
comprehend that all that we see around us—both living and non-living,
had been in existence on the earth since its beginning, only their forms
and hence activities are changed from time to time. This is the essence of
Bio-Geo-Cycles of Chemicals. Thus the above sloka of Geeta seems very
apt.
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Populations
103
Chapter VI
Populations
(The Milling Millions)
Topics
VI. 1. The Definition
VI. 2. Characteristics of Population
VI. 3. Seasonal and Annual Changes in Populations
VI. 4. Territoriality
VI. 5. Population Age Pyramids
VI. 6. Population Interactions
VI. 7. Some specific Responses of Populations to meet the
Challenges of Environment
VI. 8. Byorhythm
VI. 9. Specific Responses of Populations to Factors of Weather
VI.10. Measurement of Populations
This page
intentionally left
blank
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Populations
105
CHAPTER VI
POPULATIONS
(The Milling Millions)
“There is no exception to the rule that every organic being naturally increases at so
high a rate, that if not destroyed, the earth would soon be covered by the progeny of a
single pair. Even slow breeding man has doubled in twenty-five years, and at this rate,
in a few thousand years, there would literally not be standing room for his progeny.”
— Charles Darwin - The Origin of Species
(Avenel Books, New York, 1976, p. 117)
1. THE DEFINITION
1.1. So far we were busy in acquainting ourselves with the elementary
concepts of ecology such as, basic features of a normal ecosystem
(Chap. II); how food materials pass from one level of producers to the
next (Chap. III); how solar energy travels through the entire ecosystem in
an ever depleting manner (Chap. IV) and finally how chemical elements
travel in a cyclic fashion from the living to the non-living and back to the
living in ecosystems (Chap. V).
1.2. Arming ourselves with these elementaries of ecology we shall now
turn on our attention to the lives and activities of groups of individuals in
an ecosystem i.e. Populations.
1.3. The word Population means an assemblage of all members of the
same species living in the same ecosystem. For example, tigers of
Sunderbans of India and tigers of Siberia of U.S.S.R. from two different
populations though they both belong to the same species-Panthera tigris.
The population of Sunderban tigers is so far placed from the Siberian
tigers that they cannot interbreed. This genetical isolation of one set of
members of the same species from another is an essential requirement for
eventual evolution of a species.
1.4. From this angle Darwin’s observation given in the opening of this
chapter is very valuable. It seems to us, just as for animals, such concepts
for population increase is relevant about human species Homo sapiens as
well. More about this later when we talk about territoriality of
populations.
Definition and
Characteristics of
Population
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106
Ecology for Millions
2. CHARACTERISTICS OF POPULATION
There are some biological traits which are shared by all populations as a
group but not as individuals. There are—
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Birth Rate or Natality,
Death Rate or Mortality,
Density,
Growth Rate,
Biotic Potential,
Territoriality,
Bio-rhythm, and a few more.
Of these the first four are universal. The rest are although interesting
but more relevant in certain specific situations and populations. So we
may refer to those if and when required. Now we shall examine these one
by one.
Birth Rate or
Natality
2.1. Birth rate is the rate at which new individuals are born to a
population in an unit of time. This unit of time, depending upon the
nature of the population, may be as small as an hour or less (for instance
yeast), to as big as an year or more (for instance elephant). Birth rate is
naturally quite different from birth.
2.2. Birth is a biological process of producing one new individual from
another individual at a particular point of time. There may not be any
more repetition of such process for several succeeding points of time.
Biologists distinguish birth from birth rate by calling the latter Natality.
2.3. Natality of a population is a very important information regarding it.
For example, birth rate of dear population and birth rate of rabbit
population although both are herbivores and both inhabit the same forest,
may not be same. While natality of a population of 1000 spotted deers in
one year may be 250, that of rabbits of same number might be no less
that 500. Forest rangers use such data in the management of forest and
parks.
2.4. The capacity of producing new individuals by an individual is
however called fecundity. Fefundity varies enormously from species to
species. An elephant may produce one baby in two years, a human being
one in one year, a rat several within a few months and a cod fish may
release one million eggs in a river in one season! In this measure of
facundity however the unquestionable winner is the Pacific giant calm
Tridacna.
2.5. Like spewing of a white cloud from a volcano, one single calm
releases more than a billion eggs in water at one go—a truly “Guiness
Book of Record” performance (Fig. VI. 1)!
2.6. Later we shall see that mere size of litter or, number of eggs laid per
season do not ensure the survival of species. Much more is taken to
achieve that. Attenborough in his remarkable book (The Trials of Life:
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Populations
107
Figure VI.1 Billions of eggs being released from a single giant pacific calm Tridacna sp.
Little, Brown and Co. 1990) has beautifully shown some of the struggles
a species has to undertake to survive and breed.
2.7. All the thousands of eggs released by a fish in water or even a few
eggs laid by a bird in a breeding season do not survive. Hence natality
can be of two types. First is the maximum production of new individuals
that is possible for one individual under ideal conditions. This is called
absolute or physiological natality. The second is the realised or
ecological natality which means the actual population increase under
specific ecological conditions. Naturally ecological natality of a species is
much smaller and varies from place to place depending upon how
encouraging or discouraging the habitat is for the birth of the offspring of
that species.
2.8. Just as we have talked of birth-rate now we shall talk about deathrate or mortality. Death-rate is the rate at which a certain number of
individuals belonging to a population, die within an unit of time. Naturally
this unit of time varies according to the nature of the species. Like natality
here too this unit may be as small as one hour or less for a being like
Physiological Natility
and Ecological
Natality
Death Rate or
Mortality
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108
Ecology for Millions
yeast or as big as a year or more for a being like elephant. We know that
animals or plants which produce too many young ones or eggs or seeds
will lose most of these before they reach maturity and reproduce.
Otherwise before long, the earth will be overrun by one species
population-the one species which produce the maximum number of eggs
or seeds.
Theoretical Mortality
and Ecological
Mortality
2.9. The following table will illustrate the consequences of unrestricted
growth on two relatively slow breeding populations-man and elephant
(Table VI. 1.). In just four hundred years there would be thirty thousand
five hundred and seventeen crores of human beings and in just eight
hundred years, three thousand fiftyone crores of elephants on earth. But
this does happen not so. In any undisturbed ecosystem the relative sizes
of different populations of species remains nearly unchanged. Normally
mortality in a population is more than what it might have been under ideal
conditions ie unlimited food and space etc. This means that there is a
minimum or theoretical mortality and an actual or ecological mortality
for that species population. The theoretical mortality is always less
than ecological mortality.
2.10. Natality adds to a population and mortality subtracts from it. Also
sometimes some members of a population migrate away reducing the size
of the remaining population or, by a reverse operation ie by immigration
some new members may join the population increasing its size. So the
Table VI.1.
UNRESTRICTED POPULATION GROWTH OF TWO SLOW
BREEDING SPECIES–MAN AND ELEPHANT.
(Assumption is that man has 25 years and elephant has 50 years of reproductive
period but both pair will produce 10 offspring each, during this period.)
After year
(a) Man (25 yrs × 10)
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
10
50
250
1250
6250
31250
156250
781250
3906250
19531250
97656250
488281250
2441406250
12207031250
61035156250
3055175781250
(b) Elephant (50 yrs × 10)
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
10
50
125
625
3,125
15,625
78,125
3,90,625
19,53,125
97,65,625
4,88,28,125
24,41,40,625
122,07,03,125
610,35,15,625
3051,75,78125
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Populations
109
status of a population at any time therefore is the result of four processes
operating simultaneously on the population, prior to that time. Ecologists
show this by a very simple equation.
Status of a
population
Nnow = Nthen + B – D + I – E
When
Nnow = number now
Nthen = number then
B = birth
D = death
I = immigration
and
E = emmigration
The sum total of all these processes determine N now . When N now is
expressed against the area the population is occupying, we call it Density.
Density is usually expressed as number of individuals per unit area. The
following table shows the densities of human populations and the land
available per individual in some selected countries of the world
(Table VI. 2).
2.11. From the above table it is quite clear human densities varies widely
from country to country. Gaza strip is the most densely populated country
of the world and Australia the least, with 2744 persons per square km. or
Table VI.2.
RELATIVE DENSITIES OF HUMAN POPULATIONS OF SOME COUNTRIES AND LAND AVAILABLE
PER CAPITA THERE, ARRANGED IN DESCENDING ORDER OF DENSITY
(By H.L. Kundu from C.I.A. Data – 1999).
S. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Country
Gaza Strip
Bangladesh
Japan
India
Israel
U.K.
Pakistan
China
Syria
Egypt
Iraq
Kenya
U.S.A.
Brazil
Saudi Arabia
Russia
Canada
Australia
Population (per sq. km.)
Square Metre (Per head)
2744
871
333
294
267
241
164
127
87
65
51
50
28
19
10
9
4
3
364
1150
3003
3401
3745
4149
6098
7874
11494
15384
19608
20000
35714
52631
100000
111111
325216
416883
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110
Ecology for Millions
364 square metre of land per person in gaza and 3 persons per sq. km. or
333333 sq. metre of land per person in Australia. This is remarkable
indeed. Later we shall discuss about the reasons of this. Now let us spend
some time on Malthus who was a pioneer regarding studies on human
population ecology (demography).
Thomas Robert
Malthus
2.12. Thomas Robert Malthus (1766-1834) was born of a middle class
english family, educated at Cambridge and spent early part of his life as a
curate. At 38, he joined East India Company’s College at Hertfordshire as
Professor of History and Political Economy. His seminal book Principle
of Populations was first published in 1798. Immediately it drew
worldwide attention of scholars. The main theme of the book was whether
human society is perfectible or not. He thought not, as, the tendency of
human population is to grow exponentially while the food supply can
grow at best arithmatically. Hence this will lead to misery and vice. This
contention of Malthus was a cornerstone of Darwin’s theory on ‘The
Origin of Species’. In Darwin’s language: “A struggle for existence
inevitably follows from the high rate at which all organic beings tend to
increase............”. “Hence as more individuals are produced than can
possibly survive, there must in every case be a struggle for existence”....
“It is the doctrine of Malthus applied with manifold force to the whole
animal and vegetable kingdoms;” ... So we feel one can fairly say Malthus
was a precursor of Darwin. (Interestingly Malthus had only two surviving
children i.e. zero growth family—at a time when most of his
contemporaries used to have several children. Most Europeans who
colonised Americas soon after Columbus’s discovery of America (1492),
used to have very large families—most had more than six children).
2.13. As shown before, the status of any population i.e., Nnow is a result
of Nthen + B – D + I – E (for explanation of symbols see para 10). All the
above processes which influence the status of a population ie birth, death,
immigration and emigration are called demographic processes.
Patterns of Growth
of Populations
2.14. Any population when unhindered, tends to grow. When the size of a
population is plotted in a graph, depicting the growth of the population
from the time of its introduction to a place, at successive points of time,
we get a curve which is called as growth curve (Fig. VI. 2).
Sigmoid Growth
Curve
2.15. The above graph shows how in a favourable habitat the population
of a species tends to grow on and on until the habitat becomes fully
saturated. This means that this environment now can no longer support a
bigger population of that species. This type of growth curve which looks
like a slanted capital ‘S’ is called Sigmoid Growth Curve or, ‘S’ shaped
growth curve. This sigmoid type of growth pattern is likely to happen
with large predators in a forest or savannah—such as lions in African
savannah and also for small animals in special situations; for instance
barnacles in sea. Barnacles are a type of small invertebrate (belonging to
the groups of prawns and crabs), who remain attached with sea-side logs,
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111
Density (No. per unit area)
Populations
Time (days/years)
Figure VI.2 A simple growth curve (sigmoid curve) of population.
or stones and such stable foot-holds (Fig. VI. 3.). (The young ones of
barnacles swim about in sea, looking for a foot-hold. Once these find one
such as stone, pillar or wood etc., these quickly settle upon it and grow. In
this way when all the available space is occupied, no new barnacles can
settle upon. So here the population growth is a sigmoid one.)
Jetty
High tide level
Low tide level
Concrete
pillers
Barnacles
Figure VI.3 Barnacles attached and covering a foothold.
2.16. There is another pattern of growth where the population rises very
fast until all the available resources of the habitat is used up and then the
population plummets down or crashes (Fig. VI. 4). This type of quick
rise followed by sudden crash is found amongst many invertebrates such
as planktons in a lake. In a lake in cold place say Dal Lake in Kashmir or
lakes in Scotland, winter is so cold that planktons can no longer grow.
When summer comes and water temperature rises suddenly there is a spurt
of plankton-growth; they grow very fast and quickly use up all the
available nutrients. Soon due to lack of nutrients plankton population
almost drops to nil. As the bodies of dead planktons decompose and the
nutrients are released into water, the plankton number spurts up again.
“J” Shaped Growth
Curve
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Ecology for Millions
Density (No. in c.c.)
112
Time (days)
Figure VI.4 A “J” shaped population growth curve.
2.17. This type of quick rise followed with a sudden fall of population is
known as ‘J’ shaped population growth-as this rise and fall roughly looks
like the letter capital. Besides plankton such type of growth pattern is
generally exhibited by small animals like insect larvae, stored grain pests
etc.
Specific Mortality
Life Table and
Cohort
2.18. There are standard mathematical equations available for describing
such patterns of growth and for comparing the growth patterns of one
species with another. We may come to such equations in future, if need
be.
2.19. When the mortality of the members of a population “is expressed as
a percentage of the initial population dying within a given time” this is
called Specific Mortality. If the entire life-span of a species is devided
into several successive and equal periods and we work out the specific
mortalities of each period and put this information in a tabular form, we
get a table called Life Table.
The Life Table is a table which gives the mortalities of a species
population at each age-group. Adolf Murie an U.S. National Park Ranger
very painstakingly collected such information on the mortalities of Dall
Mountain Sheep Ovis D. Dalli of Mt. McKinley National Park of Alaska
(1944). Soon after from these data of Murie, Edward S. Deevey (1947)
prepared a life-table of these sheeps (Table VI. 3). Perhaps this is the
earliest and one of the best prepared life-tables. The symbols x, x′ , dx,
I x , 1000 qx, ex etc. are now standard notations for life-tables and
accepted symbols in demographic works. There are more such standard
notations. We are just exposing the readers with the meanings of most
common of these.
(1) ‘Specific Mortality’. The meaning of the term ‘Specific
Mortality’ is already given earlier (see para 18).
(2) ‘Cohort’. The meaning of the term ‘Cohort’ is as follows. A
group of individuals sharing a particular demographic or statistical
characteristic is called a ‘Cohort’.
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Populations
113
Table VI.3.
LIFE TABLE OF DALL MOUNTAIN SHEEP, OVIS D. DALLI
(From Odum 1959, p. 166)
x
Age (years)
0-05
0.5-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
11-12
12-13
13-14
x
dx
Ix
1000qx
ex
Age as percent
deviation from
mean length
of life
Number dying
in age interval
out of 1000
born
Number surviving
at beginning of
age interval out
of 1000 born
Mortality rate
per 1000 alive
at beginning of
age interval
Expectation of life,
or mean life-time
remaining to those
attaining age
interval (years)
–100
–93
–85.9
–71.8
–57.7
–43.5
–29.5
–15.4
–1.1
+13.0
+27.0
+41.0
+55.0
+69.0
+84.0
54
145
12
13
12
30
46
48
69
132
187
156
90
3
3
54.4
153.4
15.0
16.5
15.5
39.3
62.6
69.9
108.0
231.0
426.0
619.0
937.0
500.0
1000.0
7.06
–
7.7
6.8
5.9
5.0
4.2
3.4
2.6
1.9
1.3
0.9
0.6
1.2
0.7
1000
946
801
789
776
764
734
688
640
571
439
252
96
6
3
2.20. Reverse of mortality is survival. When the number of individuals
survived from the same age-group or cohort, at fixed time-intervals/of
their lives, are put against the time-intervals in a two dimensional graph,
we get a curve - the Survivorship Curve. Such survivorship curves can
provide valuable information about a species population such as—
(a) It can tell us at which age-group that population is most
susceptible to death,
(b) It can tell us at which age-group the population is least
susceptible to death ie strongest against environmental pressures
like predators, etc.
(c) It can also tell us at which age the vigour of youth gives way to
old age so senility begins to set in, and finally death takes over,
(d) It tells us the average life-span of members of that population.
2.21. By judicious use of such ecological information we can discourage
a pest like an insect by hitting it at its most vulnerable stage in life or,
patronise an animal or plant (which we consider useful to us) by reverse
tactics ie protecting it at its most vulnerable stage of life.
Here is an example—mosquito. Pouring kerosene oil occasionally into
pools of stagnant water where mosquito lays eggs is a very effective way
to reduce mosquito population. In order to breathe the larvae have to visit
Survivorship Curve,
its meaning and
usefulness
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114
Ecology for Millions
water surface at regular intervals. When at surface air enters the trachea
(air breathing tubes) of the larvae thus enabling these to respire. When
kerosene is poured on water it covers the water surface as a thin film and
enters the tracheae of the larvae and choke them whenever these visit the
surface to breathe. So they die of asphyxiation. Visiting water surface by
the larvae for breathing, is the most vulnerable stage in the life of
mosquito. So any control measure at that stage would be most effective.
So far kerosene is perhaps the cheapest and environmentally least harmful
tool for controlling mosquito populations.
2.22. The following figure gives the survivorship curves of a certain
species population (Fig. VI. 5). The figure depicts, based upon the
respective life-tables, the survivorship curves of Dall Mountain sheep
Ovis. D. Dalli, men from rich countries, men from poor countries. Hydra,
fishes and oysters. Each curve reflects many valuable information about
the life of that species population. In nutshell the convex curves mean
well-cared for childhood, vigorous youth and death takes over only when
the natural life-span is over. The concave curves indicate the reverse
situation ie scarce parental care so, sharp infantile mortality which
continues with lessening severity during youth and old age. Attrition starts
long before the natural life is over. Curves in between these two extremes,
indicate high mortality at all stages owing to various environmental
pressures such as, paucity of food, predation, lack of space etc. etc.
2.23. Fishes usually have very high mortality at egg and fingerling stagesmostly due to predators. Once the fingerlings acquire a certain size these
Man
(ric
h
co
un
n
n
ee
sh
p
a
ntr
ou
dr
rc
Hy
(po
o
i
ta
Ma
n
Da
ll m
ou
s)
trie
100
)
ie s
10
sh
Fi
Survivors-per thousand (log scale)
1000
r
ste
Oy
Birth (mean span of life)
Figure VI.5 Survivorship curves.
Death
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Populations
enjoy a considerably hazard-free existence till mature age. Oyster larvae
float around in sea as a part of plankton population looking for a foothold. During this period these suffer very heavy mortalities. That is why
their survivorship shown almost a vertical decline until these secure a
foothold. Once this is achieved the sessile oysters suffer few casualties.
Most grow to maturity. Hydra on the other hand, suffer from mortalities
at every stage of its life. Dall Mountain sheep whose most natural hazard
is wolf predation, suffer premature mortalities mostly at infant and young
ages, but once they attain youth these can tackle wolf and hence do not
suffer too much till they become old and weak and hence can no longer
fend off wolf attack.
2.24. Life-Tables, Survivorship Curves and fecundity schedules prepared
for discrete populations such as members of one religion or one community
or one locality etc. will yield valuable information for planners. Interestingly
such information can easily be obtained by school boys as part of their
school projects with no or little cost. Such data are of utmost importance as
these contain the raw material of ‘ecological facts of life’. Without these we
can neither understand Nnow nor hope to predict Nfuture of human beings or
specific human populations and their needs.
115
Use of Life Tables
and Survivorship
Curves in Planning
VI.2.5. Biotic Potential and Struggle for
Survival
2.25. “There is no exception to the rule that every species of organic being
naturally increases at so high a rate, that if not mostly killed, the earth would
soon be covered by the progeny of a single pair.” (Charles Darwin—1859).
Please refer to Table VI. 1. This natural propensity to increase at a very high
rate is now-a-days called by ecologists as Biotic Potential. Chapman (1928)
first proposed this term and defined it as “the inherent property of an
organism to reproduce, and survive i.e. to increase in numbers”.
Living beings require four conditions to survive. These are:
(a) food,
(b) space,
(c) breeding facility and
(d) proper weather.
If the first three are unlimiting and the fourth one is favourable then,
any living being will grow in number as fast as its physiological capacity
(i.e. physiological natality) permits. This maximum reproductive capacity
for a species in ideal situation is the Biotic Potential and is denoted by a
standard symbol ‘r’. Or in other words the symbol ‘r’ is the difference
between instantaneous specific natality rate and instantaneous specific
mortality rate. Simphy speaking r = birth – death or, r = b – d.
2.26. Though one may presume ‘r’ to be constant for a species this not
really be so. Depending upon reproduction of the component agegroups and their sizes, ‘r’ may vary from population to population of the
same species even though other factors such as food etc. may be
unlimiting. Hence there may be several values of ‘r’ for the same species
population depending upon the population structure (i.e. age groups).
Variability of ‘r’
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Ecology for Millions
When a stationary and stable age-distribution exists then the
specific growth rate is called the intrinsic rate of natural increase and
denoted at “r1 ”. At any rate whether ‘r’ or “r 1”, Nature can support
neither for long. Competition must take over to maintain balance.
Havoc from full play
of Biotic Potential
2.27. Unrestricted breeding inevitably leads to catastrophe. Here are some
examples, some estimated, some actual. Carl Linnaeus has calculated that
if, an annual plant produce only two seeds each year, even then in twenty
years it will leave a million plants! Charles Darwin estimated that an
elephant, one of the slowest breeder amongst animals, will leave in five
hundred years, from one initial pair, a population of fifteen million
elephants (pl. see Table VI.1, as well). Following table gives how
houseflies would multiply in one year, if unchecked (Tab. VI. 4). Eggs
layed by houseflies Musca domestica in just one year starting from one
pair of housefly and assuming it will lay 120 eggs in one generation of
which 50% will be females and it will have seven generation in a year
and all will live only for one year then one pair will lead to the production
of nearly 5000 billion eggs of houseflies in just one year, (E. J.
Kormondy- P. 76. Concepts of Ecology 1978. Printice Hall. New Delhi).
Here is our estimation for human beings Homo sapiens (Table VI.1).
Normally one healthy human female can produce ten children in her
reproductive life of twentyfive years of these half may be females. If
they can breed unrestricted, in a short span of 325 years, one pair of
human beings will lead to a human population of 2.44 billion human
beings-double of today’s population of China (Table VI. 6). Obviously
Nature can never permit such unrestricted breeding to any species.
When Nature is prevented from acting freely then conscientious human
intervention is the next best thing. Today human beings are the most
powerful manipulator of Nature. But limited human intervention is not
enough. Human population has never grown as fast as its physiology
permits (i.e. ‘r’). There was always some pressure on it to grow slowly.
Table VI.4.
GEOMETRIC INCREASE IN THE GROWTH OF A POPULATION OF ONE PAIR
OF HOUSEFLIES (MUSCA DOMESTICA), IN JUST ONE YEAR, IF
UNRESTRAINED AND RESOURCES ARE UNLIMITED
(Kormondy – p. 195)
Generation
Eggs laid for year
1
2
3
4
5
6
7
120
7,200
432,000
25,920,000
1,551,200,000
93,212,000,000
5,598,720,000,000
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Populations
117
Still depending upon the prevailing social customs and financial leverage,
human densities vary very widely in different countries (Table VI. 2).
Today, Gaza strip and Bangla Desh are the two densest countries in the
world, the earlier having 2744 and the latter 871 persons per square
kilometre. It seems this alarming situation is due to prevalent social custom
and access to modern medical facilities. Most Ladies have 4-8 children
but owing to availability of better medical facilities now than ever before,
infantile mortality has been drastically reduced. Earlier many children used
to die off before becoming adults from malaria, cholera, small pox and
malnutrition etc. But not today. Hence this ‘so called’ population explosion.
We shall come to these issues again the last chapter of this book.
2.28. Here are two examples of active human intervention. In Zambia
they have big elephant reserves where hunting and poaching is completely
halted. Except occasional poachers-who hunt elephants for tasks, meat,
hide and trophy, elephants have little to fear from other animals. Only
lions occasionally kill one or two calves. So in Zambian game preserves,
where rangers are mostly British or, locals trained by British, the elephant
population has risen so fast and so much that these are destroying the
forests they live upon. So, now Zambian Government regularly culls (kills
off selectively) elephants in their reserves to keep the elephant population
down to a healthy level for the ecosystem i.e. the reserves. In U.S.A. the
Fish and Wildlife Department opens up their reserve forests once every
year to permit a 2 to 4 week hunting season for deers. In November
1998 hunters in Maryland alone, killed 39,466 deers during a two-week
hunting season (Washington Post. 19-12-98). Thus a well-managed
forest is not only a pleasure to visit but can also be a source of
revenue for the forest departments. This is equally applicable for the
lakes, rivers and coral reefs of coastal waters.
2.29. “A struggle for existence inevitably follow from the high rate at
which all organic beings tend to increase” (Darwin-Origin of Species. p.
116 Avenel 1979). In a normal large ecosystem, uninterrupted from
human intervention, various internal competitions for food, space etc.
always operate. Through these mechanisms of checks and balances,
Nature prevents a species from growing as fast as its ‘r’ or ‘r1’ would
allow. These mechanisms are collectively called Environmental
Resistance. As a result of this i.e. environmental resistance, the actual
growth of a population that we find in Nature is called Ecological
Potential and may be denoted as ‘re’. If ‘re’ is one, then the population
remains stable i.e. neither increases nor decreases, if more than one than
the population would grow with time. Here are the ‘r e’s of some
populations worked out by the ecologists (Table VI. 5.).
2.30. From the above table it seems that, the population of whites in
U.S.A. will grow slowly, Calandra (a grain weevil) will grow
astronomically fast, Chorthippus (a grasshopper) will vanish soon and
Need for Intervention
with Biotic Potential
Need of periodic
culling and Well
Managed
ecosystems are
sources of revenue
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118
Ecology for Millions
Table VI.5.
THE GROWTH POTENTIALS OF POPULATIONS OF SOME SPECIES.
(Prepared by author from Odum 1963, p. 181 and Begon et al. 1990, p. 133 and 136)
1.
2.
3.
Species
Yardstick and its meaning
No.
Homo sapiens (man)
(Whites in U.S.A. in
1920)
Calandra orizae
(a beetle) (Rice
weevil at 29° C)
Chorthippus brunneus
(Grasshopper)
‘re’: (no. of times the
population would multiply
in a year)
”
1.0055
Phlox Drummondis
(an annual plant)
“R0” (No. of offspring
produced for original
individual by the end of
the cohort.*
“R0”
1.58 × 1016
Author and year
Dublin and Lotka (1925)
Birch (1948)
0.51
Richards and Waloff
(1954)
2.41
Leverich and Levin
(1979)
*Cohort: A set of offspring born during a short and fixed period.
Phlox (a flower) will grow very fast indeed. In reality however none of
these ever happened. There are many reasons and specific reasons for the
realities of life not conforming to the figures. Here suffice it to say that
these data at arrived are only from small samples; to get a realistic picture
one needs much bigger samples and data over several years.
2.31. In the following sections we shall discuss some of the various
ways with which a population meets the challenges of environment
(“environmental resistance”).
Carrying Capacity
(a) Generally any big ecosystem would be able to support a
population up to a particular size and not above it. The upper limit of this
size (or capacity), in a particular ecosystem beyond which no major
increase can occur, is termed as the Carrying Capacity of this
ecosystem for that species population. Unfortunately however we do not
have many reliable data in this area. Following is one of the few available.
(b) Around 1810 the British immigrants introduced sheep in
Tasmania. Initially the sheep population rose very fast but later growth
rate slowed down gradually till it became nil. The sheep population
reached its maximum around 1850 after which the population remained
more or less stable (Fig. VI. 6). It is a typically sigmoid growth—initially
slow, then fast but constant and then again slow and finally nil (Fig.
VI. 6). The population density at the final stage is the carrying capacity
of this ecosystem (here Tasmania) for that population (here sheep) under
the then prevailing conditions.
(c) This case of sheep in Tasmania is a special case. Here men
looked after them and there was no death from predation. As a matter of
fact to ensure the safety of their sheeps, the British immigrants to
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Populations
119
Density of sheep at the carrying capacity
2000
1500
100
50
1814
1824
1834
1844
1854
1864
1874
1884
1894
1904
1914
Years
Figure VI.6 Growth of sheep population in Tasmania and its carrying capacity.
Tasmania decimated the local predator—‘Tasmanian tiger’—Canis dingo,
the only predator of Marsupial stock. (Today tragically Tasmanian tiger is
extinct). So, save the area available for grazing, nothing deterred the
growth of sheep population. For herbivores in forests there are predators
to effect their numbers. Even then forest animals unless interfered with,
exhibit sigmoid growth. Figure VI. 7., shows how in Serengeti region of
Tanzania and Kenya, population of wildebeests Connochaetes taurinus
devastated from an outbreak caused by the disease—rinderpest, rose and
levelled off in a sigmoid pattern/(Fig. VI. 7.).
No. per sq. Km.
60
40
20
1960
1960
1980
Years
Figure VI.7 Sigmoid growth pattern of ‘wildebeests’-a common
wild animal of Tanzania and Kenya.
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120
Ecology for Millions
CARNIVORES
(Weasel)
0.001
(Caugar)
Om
(Black bear)
(Mouse)
(Vole)
ge
olia
1.0
10.0
ers
eat
ers
eat
F
(Deer)
00.1
it
-fru
ed
Se
(Squirrel)
s
ore
niv
(Fox)
0.01
s
ore
rniv
Ca
HERBIVORES
Trophic levels
Food Habits and
Carrying Capacity
2.32. Any ecosystem which does not suffer too much from human greed,
for instance, a large reserve forest, would be able to support more or
less, stable densities of different species of animals. The level of density
of a species however, depends on its food habit which means the trophic
level the species occupies in that ecosystem. Here are the densities of
some common forest animals. (Fig. VI. 8).
100.0
Biomass (kg/hectare)
Figure VI.8 Densities of some common forest animals.
Food Habits and
Space Requirements
(a) One very important lesson can be learnt from this table. The
same area of land can support much more of herbivores animals than
carnivores. For instance, one hectare can support 1.0 to 10.0 kg of deers
who are foliage eaters i.e. herbivores but the same area of land can
support only one hundreth (0.001 kg.) of caugars (animal like a leopard)
as it is a carnivore (which means it has to feed itself by killing herbivores
such as deers, rabbits etc.). For the same reason a Royal Bengal tiger
Panthera tigris—a carnivore, requires about 30 to 40 sq. miles of land to
support itself. That is why tigers live alone, save breeding season when
they pair, and ferociously guard their territories. It seems to us Indian
reserve forests are mostly too small in size to support healthy and
genetically sound tiger populations and large herbrivores such as
elephants.
Poverty and foodhabit
(b) There is another point we would like to stress upon. For a poor
and overpopulated country like India, Bangladesh etc. vegetarianism is
both ecologically better and financially less strenuous. One hectare of land
can produce much more food grains than meat. The other urgent ecosociological need for countries like India, Bangladesh, Nepal and Gaza
Strip etc. and such grossly overpopulated countries is to halt further
growth of human population by bringing down “re” to 1. More about this
later.
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Populations
121
3. SEASONAL AND ANNUAL CHANGES IN POPULATIONS
3.1. The densities of populations of many species vary widely from
season to season and for some species, from year to year.
When the densities vary regularly from season to season, such
variations are termed fluctuations for example mosquitoes, planktons etc.
Many of us have suffered from mosquito bites and have noticed how the
mosquito numbers change with season.
Seasonal Changes
Fluctuations and
Blooms
3.2. In temperate countries such as Europe and North America, during
winter planktons almost vanish from waters but as soon as spring returns
there is a sudden outburst of planktonic activities and their number rises
so fast that this phenomenon is called plankton bloom (or plankton
pulse). As there is little biological activity, nutrients in water usually
accumulate in winter. At the onset of spring when temperature is warmer
biological activity erupts and abundance of nutrients (accumulated in water
during winter) leads to plankton “bloom”. Soon the planktons use up
most of the nutrients and die; so again before the summer is over there is
some accumulation of nutrients which sets in another “bloom” just before
winter i.e. in autumn (Fig. VI. 9).
Bloom
Nutrients
Bloom
Plankton
Temperature
WINTER
SPRING
SUMMER
AUTOMN
Figure VI.9 Plankton ‘Blooms’ in spring and autumn.
3.3. In relatively simple ecosystems such as tundra, where both the
numbers of species of herbivores and carnivores dependant on them are
few. Hence densities of both populations that is predator and prey rise and
fall in a cyclic manner spanning several years. This regular and cyclic
rise and fall in the population size of a species is termed Population
Oscillation.
3.4. Interestingly this significant ecological discovery was made not
through patient population surveys by biologists, in inclement weathers
and spread over several years, but from the well kept account books of
a famous business house in Canada. From 1800 onwards Hudson Bay
Company maintained accurate records of pelts (of fur bearing animals)
Annual Changes
Population
Oscillations
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Ecology for Millions
they purchased from trappers. Their records showed clearly a cyclic
pattern in rise and fall of densities of snowshoe hare and their predator
Iynx with peaks in every 9 to 10 years (Fig. VI. 10). This is a classic
case of popu-lation oscillation.
Density (in thousands)
160
Hare
140
Lynx
120
100
80
60
40
20
1845
1855
1865
1875
1885
Years
1995
1905
1915
1925
1935
Figure VI.10 Population oscillation as exhibited by Snowshoe hare and their predator Lynx.
3.5. North Canada is a rather cold place—having tundra climate. So its
ecosystem has fewer numbers of autotrophs and heterotrophs. There is a
distinct 10.5 to 10.6 year cycle within which the population of snowshoe
hare rises and falls sharply. The population of lynx whose main food is
snowshoe hare, also rises and falls with hares’ population—closely
following it.
4. TERRITORIALITY
Tendency of one
Population to
eliminate another
4.1. Requirement of space is a must for many if not all, living beings.
Some animals such as tigers fiercely protect their territories (see earlier),
while others as some trees quitely suppress the growth of other plants in
their vicinity. Tigers claim their territories by leaving scent marks (by
urinating) on important landmarks such as trees, stones. A tree Prosopic
spicigera which is endemic in semi-arid regions of Rajasthan achieves this
by secreting some chemicals from its roots which prevent growth of
other trees near it. Basically these are some of the ways by which living
beings try to eliminate or reduce competition. More about competition
follows.
4.2. What is competition? If we think a bit we shall realise that
competition simply means the struggle between two individuals or two
populations to grab the same resource such as, mate or food etc. If the
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Populations
123
object for competition is scarce then some competitor will lose in the
struggle and be eliminated. For instance, in the mating season stags fight
each other to possess the herd of hinds around them. The loser runs
away and do not get any hind to mate with and produce offsprings. The
same thing happens with many other animals. Same thing applies with
many populations. If two populations occupy the same ecosystem and
depend on the same source of nutrition then sooner or later, the population
which is even slightly stronger will eliminate the weaker one.
4.3. G.F. Gause (pronounced ‘Gauser’) demonstrated this principle of
competition elimination through a simple elegant experiment. Gause took
two nearly identical looking one-celled Protozoans. (Protozoa is the general
name for all single celled animals). Ex. 1. Entamoeba hystolytica—the
protozoa which causes amoebic dysentery. Ex. 2. Plasmodium vivax—the
protozoa which causes malaria. Most protozoans however are harmless to
us. Gause took two species of Paramecium—Paramecium aurelia and
Paramecium caudatum. Both grow well in same type of culture—oatmeal
medium. When grown separately both showed sigmoid growth curve. If
however aurelia and caudatum are grown together in the same culture
medium, aurelia soon eliminates caudatum (Fig. VI. 11).
Gause’s Competition
Exclusion Principle
4.4. From this and other similar experiments Gause concluded that when
two species or two populations of same species having same requirements
are placed together in the same environment, then the one having slight
edge over the other will eliminate the other. This is exactly what happened
with P. caudatum and P. aurelia. Obviously P. aurelia is a shade superior
in competition to P. caudatum.
4.5. This elimination of one species or population by another allied species
or population when are in the same environment is named by G.F. Gause
as Competition Exclusion Principle (1934). So far this principle is
found to be valid in all situations of competition. This is why the more
variegated an ecosystem is from the point of view of its biotic and abiotic
components - the more variety of plant and animals it would be able to
support. This is because each species or population be it a plant or an
animal will fit within a specific ecological niche within the same
ecosystem, where it would be the most suited to survive and prosper.
4.6. There are strong social evidences to believe that Gause’s principle is
valid for human societies as well. All men want money but the supply is
not unlimited. Therefore sooner or later, in a locality of human beings
which is a social ecosystem, those group of men who are bit smarter
than the other in earning money will soon eliminate the other group. This
has happened in eastern India. Over the last two centuries or so,
businessmen from western India have gradually but steadily squeezed out
the locals from most business. Today in Calcutta-the capital city of a state
in India, West Bengal where majority speak Bengali, the moneymarket is
in the hands of people whose vernacular is anything but Bengali. This
Gause’s Principle
and Human
Societies
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Ecology for Millions
Density
(in thousands)
200
150
100
P. aurelia
50
4
8
12
(a)
16
Time (in days)
20
200
150
100
P. caudatum
50
4
8
12
(b)
16
20
200
relia
150
u
P. a
100
P. ca
u
datu
50
4
8
12
(c)
16
m
20
Figure VI.11 The principle of competitive exclusion as exhibited by
Paramecium aurelia and P. caudatum.
(a) Culture of P. aurelia alone.
(b) Culture of P. caudatum alone.
(c) What happens when they are grown together.
silent revolution is creeping into U.S.A. as well. Since Second World War
businessmen from western India and other developing Asiatic countries
are emigrating to U.S.A. in good numbers. After a few years in various
small jobs, most of the emigrees have quit jobs and plunged into business
by banding together, pooling their resources and buying out small
business. Through hard work, perseverance and parsimony they are
making steady progress. This would soon become an economic force to
reckon with in U.S.A.
5. POPULATION AGE PYRAMIDS
So far about competition. Now let us come to nature of population age
groups and their significance.
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Populations
125
5.1. When members of a population are arranged in age groups such as,
infants or children, pre-breeding, breeding and post breeding groups and
are placed one above the other, starting with infants at the bottom, we get
a pyramidal structure called Population Age Pyramid (Fig. VI.12).
VI
Post-breeding
stage
V
IV
Breeding
stage
III
II
I
Pre-breeding
stage
Figure VI.12 Population age pyramid.
5.2. Generally this pyramid looks like an usual pyramid having a wide
bottom and a gradually tapering tip. Nevertheless depending on the
relative sizes of the three stages i.e. pre-reproductive, reproductive and
post-reproductive, the pyramids may be of three types—(a) with very
wide base, (b) a tall conical one with not too wide base and (c) with a fat
middle and narrow bottom (Fig. VI.13).
Past
Post reproductive
reproductive
Reproductive
Reproductive
Reproductive
Pre Reproductive
(a)
(Fast growing)
(b)
(Stable)
(c)
(Declining)
Figure VI.13 Types of population age pyramid.
5.3. Such shape of age-pyramids are indicative of the future growth
patterns of the populations. Broadly if the pre-reproductive population is
much larger in comparison with the reproductive one then, the population
is a fast growing one (type a), if the pre-reproductive population is only
slightly bigger than the reproductive one then the population will tend to
remain stable (type b) and if the pre-reproductive population is smaller
than reproductive population then the population will shrink with time
(type c). Thus age-pyramids provide valuable insight about the future
growth of a population. Three sets of information are however needed for
accurate forecasting of the growth of a population. These are—
(a) age—pyramid,
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126
Ecology for Millions
(b) specific growth rate and
(c) life-table.
Poor & developing
countries & lessons
from China and
Singapore
Such information are very valuable for any country which wants to plan
in advance, for future vital requirements of its population such as, food,
houses, schools, jobs, hospitals etc. and also the area of forest which
may remain available to its animals and plants, in order to maintain a
healthy ecological balance between man and Nature. Any country which
instead of hard thinking and acting in time, only takes add hoc decisions
based on wishful thinking, or looking at vote bank will remain perpetually
poor and won’t have much prestige in the comity of nations. It seem to
us that developing countries like Bangladesh, Palestine, Ethiopia, Pakistan,
India, Ceylon and many others need to pay more attention to their
population age groups and future projections from these. Otherwise such
countries will remain forever poor. China and Singapore have set up good
examples to learn from.
5.4. If such population age pyramids are prepared for specific human
populations based on parameters such as economic groups, religious
groups, ethnic groups and such, one can learn a lot about the future of
such specific populations and how these will affect the future of others.
This should be a very useful area of sociological research. Interestingly,
collection of such data is neither difficult not expensive. With a little bit of
imagination and knowledge the teachers of schools and colleges may
collect and analyse such data as part of their student-projects. Such data
would be valuable aids to planners. Charles Darwin used local boys to
help him collect specimens as early as 1831—34, during his voyage in
H.M.S. Beagle to South America. Here we quote from Alan Moorhead’s
Darwin and the Beagle (Penguin, 1971, p. 106). “In one of his notebooks
he catalogued fifteen hundred and twentynine specimens, from fishes to
fungi, sent home in spirits of wine. ‘My collection of the fishes and
quadrupeds of this place is becoming very perfect. A few Reales has
enlisted all the boys in the town in my service, and few days pass in
which they do not bring me some curious creature’”. British people are
nothing if not ingenuous. Darwin too although a square fully shared this
quality.
5.5. Now let us come back to the issue in hand. Here is a Table (VI. 6),
prepared by the author from C.I.A. data, regarding area, population,
population density, population age structure, female fertility, population
growth rate, main religion and income per capita of some countries of the
world. The table should be extremely useful to anybody who would like
to know more about the status of human population of a country and its
likely use from a socio-economic point of view. It can help us in
identifying the countries with densest and sparsest populations, the richest
and the poorest countries or the countries with highest female fertility
and lowest female fertility and many other useful features.
Country
Population
Population
density
(No/Sq.Km)
Population Age.
Structure 0-14; %
15-64; % 65+ %
647,500
144,000
181,040
9,596,960
360
1,919,440
3,287,590
437,072
20,770
377,835
89,215
140,800
803,940
1,960,582
65,610
185,180
1,127,127
1,001,450
582,650
923,770
1,219,912
8,511,965
2,766,890
1,972,550
9,629,091
9,976,140
547,630
17,075,200
244,820
504,750
7,686,850
268,680
24,792,375
125,340,261
11,113,861
1,221,591,778
987,869
209,774,138
984,003,683
22,219,289
5,534,672
125,752,794
4,324,638
23,107,464
132,185,299
20,087,965
18,721,178
16,137,899
58,732,577
64,824,466
28,803,085
107,129,469
42,327,458
164,511,366
36,265,463
87,563,374
270,311,756
30,675,398
58,609,285
147,305,569
58,970,119
39,133,996
18,438,824
3,625,388
38.29
870.42
61.39
127.29
2744.08
109.29
299.31
52.44
266.47
332.77
48.47
164.12
164.42
10.25
285.34
87.15
52.11
64.73
49.43
115.97
34.70
19.33
13.11
49.46
28.07
3.07
107.14
8.63
240.87
77.53
2.40
13.50
43: 54: 3
38; 59; 3
45; 52; 3
26; 68; 6
51; 46; 3
31; 65; 4
34. 61; 5
47; 50; 3
28; 62; 10
15; 69; 16
44; 53; 3
42; 55; 3
42; 54; 4
43; 55; 2
28; 66; 6
46; 51; 3
46; 51; 3
36; 60; 4
44; 53; 3
42; 52; 3
35; 61; 4
30; 65; 5
27; 62; 11
36; 60; 4
22; 66; 12
20; 68; 12
19; 65; 16
20; 67; 13
19; 65; 16
15; 69; 16
22; 66; 12
23; 65; 12
Dominant
Religion of
population
Sunni Muslim
Muslim
Buddhist
Buddhist
Sunni Muslim
Muslim
Hindu
Siya Muslim
Buddhist
Buddhist
Sunni Muslim
Hindu
Sunni Muslim
Muslim
Buddhist
Sunni Muslim
Muslim, Christian
Muslim
Christian
Muslim, Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Christian
Fertility
per female
Population
Growth (%)
Income Per
Capita ($)
4.21
1.82
2.72
0.93
6.59
1.51
1.71
3.62
2.01
0.23
2.6
2.53
2.22
3.42
1.14
3.3
2.67
1.89
2.13
3.05
1.51
1.1
1.3
1.84
0.87
1.09
0.35
0.29
0.25
0.08
0.96
1.04
6.01
3.45
5.81
1.81
7.68
2.66
3.24
6.26
2.74
1.44
4.94
4.96
5.08
6.41
2.15
5.73
6.94
3.5
4.26
6.17
3.22
2.29
2.68
2.97
2.07
1.65
1.66
1.35
1.7
1.21
1.83
1.91
800
1,200
710
2,800
1,100
3,770
1,600
2,000
16,400
22,700
5,000
1,200
2,300
10,600
3,760
6,300
430
2,900
1,400
1,380
5,400
6,300
9,700
8,100
32,200
21,700
20,900
5,200
21,200
16,400
23,600
17,700
127
Afganistan
Bangladesh
Cambodia
China
Gaza strip
Indonesia
India
Iraq
Israel
Japan
Jordan
Nepal
Pakistan
Saudi Arabia
Sri Lanka
Syria
Ethiopia
Egypt
Kenya
Nigeria
South Africa
Brazil
Argentina
Mexico
U.S.A.
Canada
France
Russia
U.K.
Spain
Australia
New Zealand
Area
(Sq. Km)
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Populations
Table VI.6.
POPULATION, POPULATION DENSITY, RATE OF POPULATION GROWTH AND
PER CAPITA INCOME OF SOME COUNTRIES OF THE WORLD.
(From C.I.A. data 1998)
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128
Ecology for Millions
6. POPULATION INTERACTIONS: (When one Population meets Another)
6.1. Whenever we come across a plant or an animal the first question
that comes to our mind is what is it and next how many are there and
then, is it useful to us and so on. Assuming we know its name (naming
is an altogether different subject—Taxonomy), the next question we
would address ourselves to is the theme of our present subject Ecology.
6.2. Basically the abundance of a population in an ecosystem is decided by
two factors. First, its response to other species and secondly, its response
to the rest of the environmental conditions. Or, in other words, the
responses of the concerned population to the biotic and abiotic factors of
its environment. Now we shall deal with the first—when one population
meets another.
6.3. When population A meets population B then A either be benefitted (+)
or harmed (–) or need not be affected at all (0). Odum (1963, p. 226)
has elegantly summarised such reactions through a table. Here is an
abridgement of that (Table VI. 7). When population A lives on population
B by attacking and killing them by sheer physical force and then eating
them, the members of A are called the predators and the member of B
the prey. The tiger is a predator and the deer is a prey. Similarly in sea, the
shark is a predator herring fish is a prey. Also one species of prey may
be predated upon by several species of predators. As predators mainly
depend upon muscle power for hunting down the prey, so it is usually a
bigger, strong and clever animal.
The Predator Prey
and Parasite Host
relationships
6.4. On the other hand when members of population A are tiny beings
which live inside the bodies of population B, which are much bigger in
size, the A are called parasites and B hosts. The parasites gain entry into
the bodies of the hosts by various clever devices. Once inside the host the
parasites live and multiply at the cost of the host. Plasmodium vivax /
falciperum the protozoans which cause malaria are, parasites and human
beings on whom these parasites live upon, are the hosts. These malarial
parasites—Plasmodium vivax or falciparum are one celled animals (or
Table VI.7.
RESPONSES OF EACH WHEN TWO POPULATIONS COME ACROSS EACH OTHER
Population A
+
+
+
0
+
–
0
Population B
–
–
0
–
+
–
0
Relationships that emerge
A predatare and B Prey. Ex. Tiger and Deer
A Parasites and B Host. Ex. Malarial Parasites and human beings
Commercial – must for A, B not affected
Ammensal – harmful for B, A not affected
Symbiosis – both need each other
Compelition – one most affected is eliminated
Neutralism – neither affects the other
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protozoans) who enters the human blood stream through mosquito bites.
Once inside human body these reproduce very fast consuming the red
blood cells. Soon the affected person is down with malarial fever and
unless treated in time the parasites may cost him his life.
6.5. In an ecosystem, predator-prey relationship is mutually beneficial.
Predation helps to keep prey population physically fit (by removing mostly
the old and weak ones) and also by keeping its size small the predator
reduces overgrazing of the forest/grassland. The prey population too by
its paucity, helps to keep the predator population fit.
6.6. In commensalism, population A is benefitted but population B is
unaffected. Such one sided gain is found both in plant world as well as in
animal world. A climbing plant on a forest tree is an example of
commensalism. The climber gets sunlight while the tree is unaffected.
Hermit crabs in sea-shore are examples of commensalism. Hermit crabs
are crabs whose main body has no protective armour. So to protect its
delicate body it must do something. If it hides into a stationary tunnel or
burrows it may secure protection but it wont get food. So instead it looks
for a movable house. This is provided by the empty shell of a whelk (a
type of sea snail). But a mere house is not enough for a hermit crab, it
must also have caretaker. As caretaker the crab gets hold of some sea
anemones which it gently places upon the upper side of the whelk shell.
Now the hermit crab can move about safely—it has a strong house in the
form of whelk shell and guards in the form of sea anemones. In this way
the hermit crab gets protection from the sea anemone but the sea
anemone is scarcely affected (Fig. VI. 14.a). This is commensalism—the
hermit crab is the commensal.
Predator Prey
mutually conuctive
Commensalism
6.7. Another interesting example of commensalism are some small fishes
which live inside the so called mouth, with rings of armoured thentacles,
of sea anemones. Such a fish is clown fish (Fig. VI. 14.b) which darts in
and out of sea anemones without any harm. This is because the mucous
that covers the skin of this fish lacks the chemical which evokes attack
from sea anemone. So here the fish gets protection from its enemies
through its host—the sea anemone. But he host gets nothing in return.
(The tentacles of sea anemones are covered with stinging cells which
stings to unconsciousness any prey—small fishes, shrimps etc. that may
come within its reach and help the anemone to devour its prey. Clown
fish elicits no such attack reactions from the tentacles of the anemones).
6.8. In ammensalism population A remains unaffected but the population
B is harmed. A classic example of ammensalism is bread mould
Penicillium. This fungus secretes a chemical penicillin which kills off all
other fungi which may come in contact with this chemical.
6.9. By chance Sir Alexander Flemming (1881-1955) noticed that
some of the culture slides he was discarding have spots where the
microbes, which were supposed to grow, did not. Flemming, thanks to
Ammensalism
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Ecology for Millions
Sea Anemone
(a)
Conch Shell
Hermit Crab
Figure VI.14(a) Commensalism: Hermit crab inside the shell of a conch with sea anemones on the shell.
Clown Fishes
Tentacles of Sea
Anemone
(b)
Sea Anemone
Figure VI.14(b) Commensalism: A large sea anemone with small fishes inside its so called mouth.
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Populations
his knowledge, wisdom and fore sight could immediately grasp the
significance of this observation. He pursued this observation and soon
discovered that this mould secretes a chemical which inhibits the growth
of any other microbe within the ambit of this chemical. This chemical, as
it is secreted by a fungus Penicillium, he named Penicillin. Later with the
help of biochemist Sir Howard Florey and others penicillin was purified
and successfully tested on human patients. Thus Flemming’s chance
observation, and his ability to grasp the significance of this and
perseverance to follow it up opened up a new chapter in medical science
and saved millions of life.
131
Sir Alexander
Flemming and
Penicillin
(It is an irony of fate that Sir Alexander Flemming—the discoverer of
penicillin died of pneumonia in his home, without getting penicillin which
was a sure cure of pneumonia at that time.)
It is however worth remembering that “chance observations” yield,
their secrets only to prepared minds. People armed with adequate
knowledge, keen power of observation and capacity for deep thinking
only, can grasp the inner meanings of chance observations. Alexander
Flemming and Isaac Newton were such men. The “Vedic Rishis” of India
were such men.
6.10. We have now discerned many instances of ammensalism in Nature.
In semi-arid places trees secrete a chemical from their roots to the
surrounding soil which prevents the growth of other trees near it. Such
chemicals are called ectocrines (opposite to endocrines which affect the
inside of the body). In semi-arid tracts of Rajasthan / India such as district
of Jhun Jhunu, there is a tree Prosopis spicigera, which grows widely but
always sparsely. Whereever they are, they are scattered—15 to 30 feet
apart (Fig. VI. 15). The chemicals secreted by its root system discourage
other Prosopis to grow near it. The environment to Prosopis is dry
(rainfall 10 inches or so, water table 75—125’ down, and soil is sandy)
and resources are limited so, this is an adaptation for survival for the
plant. Interestingly leaves of Prosopis is the main food of camels.
6.11. Here both A and B need each other for survival as, as they supply
each other with some vital necessities of their lives. Basically in symbiotic
relationship one species becomes dependent on the other. There are many
examples of symbiotic relationships. Lichen is one such. This is an
association of an alga with a fungus. The alga provides food and the
fungus—protection. The algal cells get so intimately associated with the
fungal filaments (hyphae) that the whole thing looks like a continuous
greenish-white patch. The greenish-white encrustations which we often
come across upon the trunks of palm trees particularly, betel-nut palms in
West Bengal and Assam of India, are lichens (Fig. VI. 16).
6.12. Symbiotic relationships are also known as mutualism. There are
numerous examples of symbiosis or mutualism. Here is another. The
nitrogen fixing microbes. Plants cannot fix atmospheric nitrogen but
Symbiosis or
Mutualism
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Ecology for Millions
The hillock with
a temple on the
top of it
Figure VI.15 A rural landscape of district Jhunjhunu, Rajasthan,
India, portraying the distribution of the dominant tree Prosopis spicigera.
((Locally this hillok is known as “Pahari” which is 5/6 Km. from Birla Institute, Pilani, (Raj.) INDIA.))
A patch of lichen on the trunk of a
betel nut tree
(a)
Mark of the fallen palm frond
Algal cells
Fungal hyphae
(b)
Figure VI.16 Lichen upon the trunks of betel-nut palms.
(a) Two patches of lichens upon the trunk.
(b) A microscopic view of algae-fungi association.
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some microbes can. One such microbe is Rhizobium of the family
Rhizobiaceae. These fix nitrogen within the root nodules of leguminous
plant (i.e., peas, pulses etc.). These bacteria/microbes which are freeliving in soil, multiply when these come in contact with root-hairs of a
host plant. Apparently there is some chemical stimulant which exudes
from the root-hairs to stimulate multiplication of the bacteria. Soon the
root-hairs engulf the bacterial colony within the root tissue and as the
bacteria continues to multiply, the point of bacterial infection on the root
becomes a nodule (Fig. VI. 17).
Rhizobium colony
Vascular tissue of root
Cortex of root
A fully formed root nodule
start of a new root nodule
Root hair
Towards root lip
Figure VI.17 Root nodules formed by the infection by symbiotic bacteria on root hairs of certain plants.
There are symbiotic bacteria in the rumen of mammals, alimentary
canal of termites and many places. Let us now close the topic on
symbiosis in a lighter vein. Symbiosis is like the marriage of two
physically different beings. They may be different but they depend on
each other until “death does them apart”.
6.13. In competition population A compete for the same thing as
population B. Consequently that population which has a slight edge over
the other, however slight it might be, will ultimately eliminate the other
population from the ecosystem. The relationship between Paramecium
caudatum and P. aurelia is example of competition (see Competition
Elimination Principle or Gause’s Principle p.). If put together in same
culture medium, P. aurelia will ultimately eliminate P. caudatum. (For
more see VI. 4. paras 3, 4 and 5).
Competition
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Ecology for Millions
6.14. There is however one point which deserves special attention. The
competitive edge of a population is a joint product of physical and
physiological specialities as well as the specific environmental conditions
of the ecosystem which the population finds itself in. In one set of
environmental conditions population A may win and in another set of
environmental conditions population B may win. Here is a classic example
from Tansely (1917). English botanist A. G. Tansley, who introduced the
word ‘ecosystem’, found that two species of bedstraw Galium
hercynicum and Galium pumilum would grow in both acidic as well as
alkaline soil, if grown alone. If however these are grown together then
only G. hercynicum will grow successfully in the acidic soil and G.
pumilum in alkaline soil. Thus the winner is decided by the nature of the
habitat where competition occurs.
Later many such instances are found particularly, amongst the
intertidal fauna and flora of sea.
7. SOME SPECIFIC RESPONSES OF POPULATIONS TO MEET THE CHALLENGES OF
ENVIRONMENT:
7.1. All species of populations of living beings struggle to survive and
increase in number. Obstacles to this road to success are many. First is
interaction with other populations. These we have already discussed.
The second is unfavourable weather. These we shall now address
ourselves to. Third is finding a suitable mate.
Migration and its
Types
7.2. There are several options for tackling inclement weather. Migration
is one such. Migration can be of three types. One can be moving out
from a place with the onset of bad weather and return when the weather
becomes good again. Another can be coming into a place permanently
where the weather is more suitable and the third one can be moving
away from a place permanently where the conditions are no longer
suitable. These types are called respectively: MIGRATION (two-way
movement); IMMIGRATION (moving in permanently) and
EMMIGRATION (moving out permanently) respectively (Fig. VI. 18).
7.3. For instance, when a person goes to U.S.A. from India, and settles
there for good, he/she may be called an immigrant to U.S.A. and
emmigrant from India. Now-a-days we know of many species of
animals-ranging from insects to mammals, who in order to take advantage
of climatological changes or in search of fresh pasture etc. migrate long
distances travelling from hundreds to thousands of miles. We shall briefly
touch upon these.
(1) Insect
(2) Fish
(3) Reptile
(4) Birds
(5) Mammals
–
–
–
–
–
Locusts of Sind, Pakistan.
Eels of Great Britain.
Ridley’s turtle of India.
Arctic terms.
Wildebeests of Africa.
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GOING
2
INTO
Immigration
A
GOING
PLACE
OUT
Emigration
3
GOING TO
AND FROM
Migration
1
Figure VI.18 Three possible types of movements of living beings between two places.
7.4. Locusts Schistocerca gregaria
Locusts are a species of large grasshoppers ( 3′′ or so long), (Fig.
VI. 19), often met with in small numbers in agricultural plains throughout
Asia and Africa. Since ancient times, both in Egypt as well as in China,
epidemics of locusts outbreaks have been recorded. During such
outbreaks these fly as huge marauding swarms flying over large tracts of
Migration of Insects:
Locusts.
Head
Thorax (or notum)
Fore wing (or tegmina)
Hind wing
Abdomen
Figure VI.19 A locust Schistocerca gregaria and his external features.
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Ecology for Millions
agricultural lands defoliating all vegetation that come in their way and
leaving famines in their wake.
Phase Theory of
Uvarov
Sir Boris Uvarov (1921, 28) has made a detailed study of locusts
and unravelled many aspects of their biology. Locusts have two distinct
phases solitary and gregarious. These are characterised with conspicuous
physical differences. Uvarov showed that non-migratory locusts have
swollen thorax whereas the thorax of migratory ones are somewhat
constricted like the waist of a lady (Fig. VI. 20). There are differences in
colours as well. This explanation is known as Phase Theory of Uvarov.
The solitary phase locusts are residents in their normal breeding areas but
if in some year, owing to various conditions, such as meteorological or
flooding etc. the breeding ground (also called outbreak area), gets
restricted or disturbed or crowded etc. the young locusts develop into
gregarious phase, and their populations burst into thousands of times—
literally into hundreds of millions and start their migrations of thousands
of miles. While on flight these locusts halt frequently to rest, feed and
breed. Any greenery that comes into their path—leaves, grains, crops—
all is eaten up. When locusts migrate these leave at their wake only
devastations and even famine. Here is a map of one such outbreak and
migration of locusts on Indian sub-continent in recent times (Map. VI. 1).
The outbreak centre is in Sind of Pakistan hence these migrate to
northern India and finally return to the area of outbreak.
Nobel Laureate, Pearl Buck in her novel “Good Earth” (1931) has
given a striking description of a locust migration in China. Here is how
she writes”.
“There came out of the south one day small slight cloud, ... except it
did not come hither and thither as clouds blown by the winds do, but it
stood steady until it spread fanwise up into the air.”
...........................
...........................
Then the sky grew black and the air was filled with deep still roar of
many wings beating against each other, and upon the land the locusts fell,
flying over this field and leaving it whole, and faling over that field, and
eating is bare as winter. .................
Wang lung was furious and he beat the locusts and trampled on them
and his men flailed them with flails and the locusts fell into the fires that
were kindled and they floated dead upon the waters of the moat that
were dug. And many millions of them died, but to those that were left it
was nothing.”
...........................
(Pearl S. Buck – The Good Earth; 1931 Pocket Books – New York,
London, Singapore; pp. 168–169.
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(a)
(b)
Gragareous phase
Solitary phase
(b)
(a)
Figure VI.20 The external differences between a solitary phase locust and a gregarious phase locust.
Outbreak area
IN
D
CH
IN
A
TI
BE
T
NE
PA
L
IA
PAKISTAN
BANGLADESH
INDIA
Route of
Migration of
Locusts
B
U
R
M
A
CEYLON
Map VI. 1 Map of one outbreak and migration of locusts in recent times in India.
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Ecology for Millions
elvers
young eels
Mature
eels
ells larva
Sarg
ATLANTIC
OCEAN
EU
RO
PE
H
RT ICA
NO ER
M
A
eggs
Figure VI.21 Lifecycle and migration of European cells, Anguilla viridis.
Migration of fishes:
Eels
7.5. Some of the fishes migrate hundreds of miles to feed, grow and
spawn. Eels, Salmons and Tunas are some famous examples. European
eels (Anguila viridis) live in rivers and lakes of Europe but migrate
through the deep waters of the Atlantic into the warm waters of Sargasso
Sea near Florida, to lay. The hatchlings are about half an inch long, leaflike semi transparent larvae. These feed, elongate and swim along with
the warm waters of Gulf Stream towards Europe. Within 2-3 years the
larvae become long (20-25") slim elvers. The elvers swim into the rivers
and lakes of U.K., Europe and Black Sea. There these feed for another 2
to 3 years and grow into tall 3 feet or so, thick dark and mature eels. The
mature eels then embark on the perilous return journey through the
Altanic to Sargasso Sea only to lay eggs and die (Fig. VI. 21). The
odyssey of the Salmon is equally exciting.
Perhaps through a combination of genetic information-pool and the
quality of water and environment (and may be smell of their parents’
bodies) something gets imprinted into the memory of the young eels,
which guide them unerringly, from its birth place in sargasso sea through
their entire path of migration three the seas la kis and risurs high in the
mountain valleys and back to the sargasso sea to spawn just as their
mother did—a perilous and marathon round trip of 14,000 miles in 6-8
years. This is indeed a most remarkable phenomenon of Nature.
Migration of Reptiles:
Olive Ridleys
7.6. Ridley’s sea turtles also called Pacific olive Ridley Lepedochelys
olivacea, make a spectacular annual migration for laying eggs, from
pacific ocean to Bhittarkanika in Orissa, India. Every year mearly 200.000
or more Ridleys swim up, to nest and lay eggs, in a 5 km. beach at
Bhittarkanika, for a period of only one or two days. Now Govt. of
Orissa has declared Bhittarkanika beach a protected area so that, Ridleys
can lay eggs without interference.
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Green
Land
ASIA
North
America
AFRIKA
SOUTH
AMERICA
AUSTRALIA
ANTARCTICA
Figure VI.22 Migration of Arcitc Tems Sterna paradisaea.
7.7. Birds on wings are freest of all. Who is not enthralled watching the
leisurely effortless soaring of vultures high above the sky? Still all these
have a purpose.
Migration of Birds:
Arctic tern, Golden
Plover and Snipe
Landsborough Thompson describes bird migration as “Changes of
habitat periodically recurring and alternating in direction, which tend to
secure optimum environmental conditions at all times.” Many birds
migrate. In India snipes, ducks, geese, cranes and others are common
visitors in winter. Bharatpur bird sanctuary and Calcutta Zoo are some of
the delightful places to visit in winter for birds.
Amongst migrating birds the most spectacular is the Arctic Tern
Sterna paradisaea. This bird travels from its arctic breeding grounds to
the antarctic pack ice and back each year—10,000 miles each way! (Fig.
VI. 22). Arctic Terns however, unlike many other migratory birds, feed on
their way. The eastern Golden Plover Pluvialis dominica which is a
winter visitor to India flies non-stop at least 3200 km. across open sea.
Another is the Snipe Capella hardwickii which breeds in Japan and
spends the winter in Australia travelling non-stop 4800 km. over the sea.
7.8. Mammals also migrate, long distance, from season to season, in
search of suitable astures. One classic example of such scasonal
migration is that of wildebeests—Chonnochaetes taurinus. These are a
type of large deers (like “Nilgais” of India), which travel long distances
between Serengeti plains in north-west Tanzania to Masai Mara steppes in
north-east Tanzania and south-east Kenya a distance of about 400 kms.
En route wildebeests swim through the ferilous Mara river full of large
crocodiles and throughout this journey they are harassed and killed by
lions and cheetahs. This annual odyssey consisting of hundreds of
Migration of
Mammals:
Wildebust of Africa
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Ecology for Millions
thousands of wildebeests and zebras Equus burchelli, is a spectacular
event which attracts tourists from all over the world. This may be noted
here that from tourists who come from all over the world to witness this
spectacular migration. Tanzania and Kenya Govts. earn handsome foreign
exchange.
Migration vs Vagility
7.9. Unlike animals which can move plants are sessile—i.e. fixed to a
place. So these depend on others for movement. For example air is the
carrier of cotton seeds; pasture animals carry seeds of grass and weeds
along with their fur, water currents of sea carry cocoanuts far and wide,
birds carry the seeds of plants along with their food and drop them
elsewhere along with their droppings. Many seeds have special coats
which can withstand digestive juices of birds. To facilitate such type of
movements plants have developed various adaptive devices as well. In fact
some plants have coated their seeds with such coverings that such seeds
won’t germinate till these pass through the digestive canal of a mammal
or a bird.
7.10. Such movements by plants through their seeds etc. which depend
on others is called VAGILITY in contrast with movements of animals,
which are self-dependent, is called MIGRATION. Anyway whatever is the
purpose the aim is the same—movement from here to there.
8. BIORHYTHM
(Adaptive devices other than Migration and Vagility)
HIBERNATION:
Ectotherms,
Endotherms.
8.1. Besides moving out when the weather in inclement and returning
along with good weather, animals and plants resort to various other
adaptive devices to tackle inclement weathers without moving away
elsewhere. Collectively these are termed Biorhythm. Here are some of
such devices.
8.2. Hibernation is a physiological device adopted by vertebrates (animals
with backbones) to tide over winter cold. During winter when cold sets
in and land is, at places, snow covered, many warm blooded animals
such as rabbits, bears etc. enter into specially constructed burrows and
undergo a deep winter sleep. Such winter sleep is called hibernation.
(During 1998 when I was visiting my daughter in South Riding. North
Virginia, U.S.A., there was a family of five rabbits which used to stay in
an adjacent wooded spot, behind her back garden and feed on the grass
of the lawn. When winter came and snowing began they all vanished.
Presumably these were all hibernating in their warrens. When the spring
came they were seen capering about. There is one point however which
is worth mentioning. During winter once in 15 days or so the rabbits
used come out, run about for a while and then vanish for another 15-20
days). Like rabbits other mammals such as hamsters (a type of squirrel),
bears, foxes and all those who live on cold, snow-clad places like north
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U.S.A., Canada and northern Europe hibernate. During hibernation the
heartbeats of animals go down remarkably. For hamsters the heartbeats
drop from more than a hundred a minute to merely ten or so. The
hibernating bears do not even defecate or urinate—the entire body waste
is recycled. Thus the hibernating animals conserve energy.
Cold blooded animals such as frogs, snakes etc. also hibernate during
winter.
Warm bloodedness and Cold bloodedness. Animals whose body
temperatures remain constant in all seasons are called warm-blooded
animals or endotherms. These are mammals and birds. Animals whose
body temperatures fluctuate along with that of air are called cold-blooded
animals or ectotherms. These are amphibians and reptiles. That is why
in winter crocodiles come out of water and busk in sun. This is the
reason why frogs, lizards and snakes are active in summer and during
winter these hide in their burrows or holes and remain inactive.
8.3. Just as hibernation is for tiding over winter cold similarly, aestivation
is a physiological device to tide over summer heat and drought. Lungfishes (fishes which besides gill also have lungs) of Australia has adopted
this device. Protopterus—a lung-fish of Afrika, live in ponds which dry
up in summer. So when summer comes Protopteruses make cocoons
whose insides are made waterproof through their own mucilage and
remain curled up within these cocoons till rains begin (Fig. III. 9).
8.4. Diapause is an overwintering device frequently adopted by
invertebrates (animals without backbones) particularly insects. Eggs of
Chinese silk worm Bombyx mori do not hatch out in winter. Instead
these become dormant-undergoing only various internal developmental
changes—and hatch out in the spring. This phase of winter-dormancy is
known as diapause. Also, the internal changes during diapause (which is
must for successful hatching of eggs after winter) is called diapause
development.
AESTIVATION
DIAPAUSE
8.5. This overwintering device is so compulsive for Chinese silk worms
that, even in a warm country like India, Chinese silk-worm eggs have to
be put in frigidaire so that these can undergo proper diapause. If this is not
done the larvae will be defective. Besides silk worms many other insects
undergo diapause—some as eggs, some as larvae and some as pupae.
8.6. In dry seasons small aquatic invertebrates such as Rotifers form
CYSTS—small granular things with a thick strong shell, and stay in such
dormant state for months, even years till proper weather returns. Cysts
are small and so resistant to weathering that, these easily get windborne
and carried from one water hole to another.
The above are only some of the adaptive devices. There are many
more.
ENCYSTMENT
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9. SPECIFIC RESPONSES OF POPULATIONS TO FACTORS OF WEATHER
9.1. Soil, Atmospheric Gases, Light, Temperature and Humidity are five
important environmental factors. Of these soil and atmospheric gases are
relatively stable for a locality but the other three are not. Here is a brief
discussion of the effects of these three variable factors on populations.
LIGHT SEE 3.1
9.2. LIGHT particularly sunlight is the single most important factor on
which life depends. If sun is not there life on earth will cease to be.
Elsewhere in this book (Chap. IV.) we have already discussed in some
details the relationship between sunlight and productivity. Here we shall
mention a few of the interesting behavioral and physiological adaptations
which living beings have evolved to co-ordinate rhythms of their lives,
using sunlight as guide.
Diurnal, Nocturnal
and Crepuscular
activity
9.3. Generally some animals are active during daytime, some during
nighttime. Those which are active during day are diurnal and those
during night are nocturnal animals. Deers, monkeys and crows are
diurnal and tigers, jackals and bats are nocturnal. There are others of
both groups. Again there are some who are in between the two i.e. these
are active only in the early mornings or at sun-downs. These are
crepuscular. Rabbits and partridges are some of this group.
Circadian Rhythm
9.4. There is still another group of small animals who show vertical
movement between night and day. This is called circadian rhythm. For
example, planktons in the sea come to the surface layers only during night;
during day these move down to the much deeper layers of water. Similarly
in grassfields, grasshoppers move up to the top layers and hop about during
daytime but in the nights these crawl down to the ground surface and rest.
BIOLOGICAL
CLOCK
9.5. Have you ever thought what guides the cyclic rhythm of activities of
living beings? What guides the forest to prepare for the fall? Who
instructs the cuckoos to begin his search of mates by calling? Who
informs the birds—terns in the arctic zones that winter is coming, you
better get ready to migrate to the south. What brings the tasty ‘hilsha
fish’ Clupea ilisha unerringly from the sea into the river Ganga of Indian
peninsula in every monsoon. There are many many such animal activities
which are repeated with meticulous timings every year.
9.6. Some stimulus from Nature which follows a constant rhythm from
year to year must be the guiding agent. This is SUNLIGHT. All living
beings must have a cycle of biological activities which guide their lives.
This is Biological Clock. This biological clock is powered by Light
which is the most dependable stimulus from Nature. The rising and
setting of sun at each point of earth is pre-determined and calculable. The
period of daylight or, the reverse of it ie night length, is the spring of all
biological clocks. All rhythms of biological activities of all living beings
such as, migrations, egg layings, flowerings etc. in all places of Earth are
hitched upon this most dependable guide of Nature sunlight.
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9.7. Sunlight through the photoreceptor eye, activates pituitary glands of
animals. From pituitary a chain reaction starts which finally initiates
activities such as, migration, egg laying (oviposition for insects) etc.
Pituitary however cannot be the only receptor. Plants do not have
pituitary glands. So plants and others have other photoreceptors which we
need not go into here.
9.8. Besides sun moon also initiates biological rhythms. Some marine
worms (invertebrates) which live inside tunnels in mud on the floor of
shallow seas come out of the mud regularly following the lunar cycle, to
mate. This mating period has been imprinted in heir genetic make-up so
much so that, if kept in aquarium within laboratory where there is no
moon, these still follow the same lunar rhythm according to the dictates
of their genetic make-up. Rachael Carson put has this beautifully in her
book “The Living Tide”.
LUNAR CYCLE
9.9(a). Relative Humidity (RH) or better still Vapour Pressure Deficit
(VPD) is a very important factor in determining the locations of animals
particularly those who are susceptible to desiccation. All readers however
may not follow the relations between RH and VPD. Hence the following.
See also III 6.5.2.
MOISTURE
SEE 3.2
Here a few words about atmospheric moisture would be relevant.
One litre of air at 20°C will require 20 gm. of water to be fully saturated
when its relative humidity (or RH) will be 100%. At 10°C the same 1 litre
of air will need only 10 gm. of water to saturated (i.e. 100% RH) and
similarly at 30°C, 30 gm. of water for RH 100% of so on.
Relative Humidity
(RH) and Vapour
Pressure Deficit
(VPD)
(b) If however the reverse situation arises i.e. the temp. is 10°C and
the water is 20 gm. then the air will not only have 100% RH but 10 mg.
water will be surplus so this will be deposited as dew. This is why
sometimes in the morning when the temperature is low there is dew on
grass. If no the other hand, the temperature of air is 30°C and the water
content is 20 mg. then the RH of the air will be 2/3rd. of 100% ie 66%
or so. This is the relationship of relative (RH) with the temperature (temp)
and moisture content of air.
(c) The water vapour of air, like other gases , exert pressure. This is
vapour pressure. 20 gm. of water vapour exerts (about) 20 mg. pressure;
10 gm. 10 mm. and so on. This means the more the vapour content, the
more is the vapour pressure. Or in other words, the vapour pressure and
water content bears a direct relationship with each other. The air at 10°C
can hold a maximum of 10 mg. of water; at 20°C 20 gm. of water and at
30°C 30 gm of water as water and so on. consequently if any sample of air
contains less water vapour than what it can hold, liquid water in this air will
tend to evaporate. On the other hand, if any sample of air contains more
water vapour than what it can hold, the surplus water vapour will condense
in the form of dew. Vapour Pressure Deficit (VPD) is the difference
between the pressure of maximum water that a sample of air can contain
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and the pressure that is being actually exerted the amount of water that it
holds. For example if a sample of air at 20°C holds only 10 cc. of water
then its VPD is 10 mm. of mercury (Fig. III. 13).
(d) Consequently the higher the VPD of a sample of air is, the faster
will be the evaporation of water in that sample of air. Hence in hot and
dry climate clothes dry quickly as the VPD is high, but not so in wet
season as VPD then is very low or nil.
9.10. After the above paragraphs explaining RH and VPD, we are coming
back to the effect of moisture i.e. 3.2. Toads and frogs (amphibians) do
not stay in desert sand—dunes and similar dry places. This is because their
skins (technically known as integument) are soft and very susceptible to
draught. Lizards and snakes on the other hand, can easily live in dry
sandy places. Their skins are covered with waterproof scales. So
amphibians can live only in places with high RH or low VPD but the
reptiles distribution is not tied up to such factor.
Adaptations of
Plants and Animals
living in dry places
9.11. Hence in desert or semi-arid areas (i.e. areas with high VPDs) water
dries up so quickly. Consequently there, plants and animals in such places
often suffer from desiccation. In response to such environmental pressure
these life forms develope, according to their natures, physiological,
morphological and behavioural adaptations. Plants reduce the leaf surface
and some convert leaves into thorns such as cactus. Animals develop
water-proof skins. Reptiles and birds have developed waterproof scales and
feathers respectively to cover their bodies. Amphibians who have no such
devices available are scarce in semi-arid areas. Mammals however through
their superior intelligence, have developed special behavioural adaptations to
take care of VPD problems. The common land invertebrates such as
insects and spiders have developed waterproof layers on theirs skin (also
called integument). This layer is a special type of wax. So abrasion of their
skin exposes these to the hazards of desiccation (or VPDs). Rest of
invertebrates such earthworms and snails etc. who cant resist desiccation
stay only in the moist places such as soil or, under the bark of trees. Thus
living beings tackle challenges of desiccation.
9.12. There are various other challenges living beings have to face and so
develop equally variegated ways to handle them. David Attanborough in
his book “The Trials of Life” (Little Brown and Co. 1990) has described
these beautifully with excellent photographs.
Here is a summary table of the responses that animals adopt to meet the
various challenges of environment (Table VI. 8).
10. MEASUREMENT OF POPULATIONS
(Also see III. 3.6.)
10.1. No study of population can be very meaningful until the size of the
population can be assessed. Only after knowing the size of a population
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Table VI.8.
RESPONSES AND ADAPTATIONS OF ANIMALS (AND SOME PLANTS) TO MEET
SOME OF THE CHALLANGES OF THE ENVIRONMENT TO ENABLE
THEM TO SURVIVE AND BREED
Challenges/Stimuli
Adaptations — Behaviour and Anatomical
Food
Migrations
Temperature
Water
Humidity
Light (a) Sunlight
(b) Moonlight (moon phase)
– Fishes (eels, salmons, tuna, etc.) etc.
– Birds – Arctic terns, etc.
– Mammals – Wildebeests, etc.
Hibernation – Rabbits, Hamsters, Bears of North America etc.
Diapause
– Silk worm
Aestivation – Lung fishes
Encystment – eggs of wireworms
– eggs of rotifers
Microenvironments – Earthworms, frogs, fishes with accessory respiratory organs,
Wilting of plants; Leathery and waterproof (glabrous) leaves; Thick water storing
trunks of large desert cacti, etc.
– Biological Clock (Day length or Night length)
– Initiates migration of birds, egg laying of birds, flowering of plants.
– Vertical migration in grasshoppers and planktons
– Initiates egg laying of many marine invertebrates.
we can assess as to how much it is contributing to the primary
productivity (if autotrophs) of the ecosystem or, costing the ecosystem to
sustain it (if heterotroph) and so on.
10.2. For example, a single banyan tree Ficus bengalensis which is an
autotroph and require only 1000 sq. m of land as so can support dozens
of birds, thousands of insects and thousands of worms. But one single
tiger Panthera-tigris which is an haterotroph require about 30 or more
square miles of land to provide it with enough food such as, deers, boars,
etc. Similarly one elephant Elephas loxodonta/indica will require nearly 5
or more square miles of forest to provide it with enough vegetation to
live. Hence an ecologist needs to know the size of a population, its food
habits and other essential requirements, to assess the impact of the
population on the ecosystem it belongs to. For forest rangers such
information are very vital. If in a forest there are too many predators, the
prey population will be so much depleted that the forest will overgrow
leading to the starvation and death of predators. Again if there are too
much prey and too few predators, soon the forest will be overgrazed and
destroyed. So a harmonious balance between the two is essential for
healthy ecosystem. Hence the measurement of the populations are must.
10.3. The techniques of measurement of a population will naturally depend
upon the nature of the species concerned. For instance if one counts
tigers the way one counts trees, the consequence will be very unpleasant
indeed if not tragic. So the techniques would have to vary. Here are some
common techniques.
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10.4. Quadrat Method. This is generally used for primary producers
such as grasses, shrubs and trees—which are stationary. A quadrat is an
area of 1 m2, 2 m2 or even 5 m2 or more in size (Fig. III.2). The actual
size of the quadrant will have to be decided by the ecologist taking into
account the nature of the species population and also his own angle of
study. After deciding the size of the quadrat the number of specimens
within that quadrat is counted. Several such quadrats in different
locations, within the same ecosystem, are taken at random and the
number of individuals within each are recorded. By manipulating all these
data statistically the population is measured.
CAPTURE
RECAPTURE
METHOD
10.5. Capture—Recapture Method. For populations with very large
number of individuals particularly mobile ones such as, insects, birds etc.
this method seems more suitable. Here all insects that can be captured in
a day (through nets) or in a night (through light-traps) are marked and
released. Next day again these insects are captured from the same spot in
the same method. Some of these would be marked. Now through simple
calculations one can work out the size of the population. Those who
want more information on such techniques may consult T.R.E.
Southwood (Ecological Methods, Chapman and Hall. 1978.).
INDICATORS e.g.
PUG MARKS,
SPOORS etc.
10.6. Indicators e.g. Pug Marks, Spoors etc. For large animals which are
both mobile and aggressive, indicators such as foot prints (pug marks) or
spoors (tracks) etc. are usually employed by forest rangers. Tigers, Lions
and Elephants are mostly studied in this way. This naturally requires
courage, patience and very keen power of observation. Experts in this line
can not only distinguish marks of one from the other even they can tell the
age, sex, state of health of the animals and time of the marks.
10.7. When Charles Darwin was travelling in South America as a
naturalist in H.M.S. Beagle in 1830s, he gave an accurate description of
such capabilities of some South American soldiers along with the very
cruel end of individuals thus tracked (Darwin and the Beagle—Alan
Moorehead. Penguin. 1971. p. 122-3). Here is an example. One General
Rosa of Argentina a very competent horseman was in charge of
subduing the hostile Indian tribes of pampas (Argentine grasslands).
“One day it was reported that one of Rosa’s outposts on the route to
Buenos Aires had been wiped out by Indians. So a commandant named
Miranda was ordered to go out and take reprisals”... “In the morning the
men were set off for the scene of murder, with orders to follow the
rastro or track even if it had led them to Chile. They were experts at
deciphering a track; from examining the prints of a thousand horses they
could tell how many were mounted, how many loaded; even by
unevenness of the hoof marks, how tired they were. These men would
penetrate to the end of the world”. He heard later that the raid was
successful. “In the end some hundred and ten men, women and children
were rounded up. All the men who were not likely to be useful as
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informants were shot. The better looking girls were set aside to be
distributed amongst the soldiers and later on the older women and the
uglier girls were murdered. The children were taken off to be sold as
slaves.” “Among the prisoners who were spared there were three
particularly fine looking men, all very fair and over six feet in height.
They were lined up for interrogation and when the first refused to divulge
the whereabout of the rest of the tribe he was shot dead. So was the
second and the third had no hesitation either. ‘Fire’ he said ‘I am a man,
I can die’. “Darwin was horrified, but there was little he could do except
to confide to his diary the thought that these Christian soldiers were
much more savage than the helpless pagans they were destroying.”
10.8. Tagging. Tagging the individuals members of a population with
special markers such as, rings on legs, radio collars, implementing radioactive device under the skin etc. etc., are some of the devices resorted to
by ecologists and behaviour scientists. These techniques have proved very
useful in studying migrations of birds, marine turtles etc. There are many
other methods which are being constantly developed and used by
ecologists of today, depending upon the nature of the target population and
level of resources available and above all their knowledge, ingenuity and
wisdom. So ingenuity and common sense of the ecologist are most
important aids in measuring or assessing a population.
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Chapter VII
Community
(The Noah’s Arc)
Topics
VII.1. The Definition
VII.2. Dominance
VII.3. Succession
VII.4. Ecological Niche
VII.5. Balance In Community
VII.6. Approaches To Community Study
VII.7. Space and Carrying Capacity
VII.8. Phases of Human Civilisation
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CHAPTER VII
COMMUNITY
(The Noah’s Arc)
“Two hermits can live on the same blanket but two kings cannot stay in the same
Kingdom.”
.............. an old Indian proverb
1. THE DEFINITION
1.1. So far we were talking about the individual populations i.e. members
of a single species. An ecosystem however is never made of a single
population but consists of an assemblage of several interacting and
interdependant populations and the sum total of whose functions
determine the personality of a community.
Definition of
Community
1.2. All the populations of an ecosystem—both autotrophs and
heterotrophs when taken together, form a COMMUNITY.
1.3. Different ecosystems would therefore appear to be different from one
another in looks. For instance, an African savanna mainly has grasses and
a few trees whereas the rainforest of Mudumalai hills of Kerala, India,
consists mainly of trees and undergrowth. This means a savanna is
dominated by grasses and a few scattered trees while a rainforest is
mainly dominated by a dense assemblage of trees.
2. DOMINANCE
2.1. Any community when taken an overview of, will appear to be
dominated by one or a few species of autotrophs and heterotrophs, either
by their number or size or both. Basically this means any species or group
of species which plays a major role in flow of energy in community is
considered the dominant species or the dominant group of species of that
community. These dominant populations tend to lend a personality to that
community and hence the community is named that way. For example, the
tropical savanna of Africa may be named as Grass-Tree Community
while the rainforest of Mudumalai Hills, Kerala, India may be named as
Tree-Undergrowth Community (Fig. VII. 1).
Naming of a
Community and
Dominant
Populations
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Top of a big tree
(in direct sun-light)
Canopy
Shrubs growing under
big tree (in semi shade)
Understory
Soil
Figure VII.1 A tree-undergrowth community.
Mangrove
Community
2.2. In India, the Gangetic delta, where the river Ganga meets the sea,
has an extensive mangrove forest of around 2585 sq. km. This is a zone
with vast tracts of intertidal areas having only a few plant species most of
which have air breathing roots or pneumatophores. These trees are
generally called mangroves and the community Mangrove Community.
Pine-Deodar
Community
2.3. The Himalayan hill region however ranging from 5000 to 8000 ft.
altitudes, are mostly covered with pine and deodar trees as the dominant
trees. So these can be called Pine-Deodar Community.
Other Communities
2.4. In between these two communities i.e. the mangrove community in
the delta of river Ganga and the pine-deodar community of the Himalayan
hills, lie the vast tracts of plain lands and other hill regions of India. These
are dimonated by various other types of communities. We shall come to
these later if, and when necessary.
3. SUCCESSION
Invasion of Life and
Evolution of a
Community
3.1. Nature abhors vacuum. Any place on earth if, for some reason is
devoid of life, will, at the first opportunity, be filled up with living beings.
Here is an example. During volcanic eruption hot molten lava comes out
from the volcano and covers the slope around it. Because the lava is a hot
molten liquid it is not only devoid of life, it also kills off all living beings
around the rim of the volcano and all the slopes covered by this hot liquid
volcanic lava. So after such a volcanic eruption the sides of the volcano
become a lifeless and barren landscape—no grasses, no trees, no
insects—nothing. But as soon as the lava cools down it starts getting
covered with various life forms—first plants and later animals. This is an
invasion of life into a lifeless but life-supportable environment. There
can be many such examples. Here is another. When a new island comes
up in a river delta, it is just a flat alluvial land very near the level of the
surrounding river water but lifeless. But soon this new lifeless and deltaic
island start becoming covered with living forms—first by plants followed
by animals.
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3.2. Most of the southern part of West Bengal of India and Bangladesh
have been formed in this way—i.e., by deposition of millions of tons of
alluvial soil brought down through thousands and thousands of years by
the mighty rivers Ganga and Brahmaputra, from Himalayan mountains.
3.3. All the plants and animals which thus occupy a new area, together
form a COMMUNITY. Such newly established communities do not
remain same for long. Changes in the ecosystem brought in by the first
community will lead to the replacement of the original community i.e.,
this first community by a new set of plants and animals i.e., a new
community. With time this second community will also give way to a
third comunity and even more till, after many years, a stable ecosystem
gets established in that area. This stable ecosystem has a tendency to
maintain its structure (i.e., nature of its plants and animals association) for
a long time afterwards (unless disturbed by man or other natural
calamities). This invasion of an area by living beings through distinct and
successive communities of living beings is called SUCCESSION. This
succession leads to evolution of communities.
3.4. The first stage of evolution of a community is called the PIONEER and
the final stage of evolution i.e. the stage—where the ecosystem has become
a self sustaining and relatively stable one, is called the CLIMAX. The stages
in between are called the SEERS. So the pioneer, the seers and the climax
are the three definitive stages in the evolution of a community and also
ecosystem (The word ecosystem however, means much more than a
community. A community is only a part of an ecosystem.) This evolution
of a community is a long and slow process taking at least 150 years or
more and hence not very easy to observe and study. However, the shorelines
of a big natural lake which is gradually drying up offers an excellent
opportunity for such study (Fig. VII. 2.). In the shoreline of such a lake an
ecologist can visualise all the stages of community evolution—i.e. from the
pioneer, through the seers till the climax—all simultaneously. So in ecology
succession means the process of evolution of communities.
3.5. The shores of Lake Michigan, U.S.A. offer an opportunity for such
study. Once, long ago, Lake Michigan had a much bigger area than today.
As the lake shrunk with time, more and more shore areas got exposed and
became available for invasion by plants and animals. Hence here an
ecologist can observe all the stages of succession. The tier of flora and
fauna which are nearest the water-line is the area most recently invaded
by living beings. So this is the pioneer stage and as the ecologist moves
away from water-line he comes accross the first seer, then second seer and
so on till the ecologist reaches the tier of flora and fauna which merges
indistinguishably and permanently (i.e. without any further changes) with
the neighbouring large ecosystem. This is the climax (Fig. VII. 2.).
3.6. Another place on earth-where one can find such stages of evolution
of an eosystem is the volcanic lava slope created by the recent huge
Stages in Invasion
or, Succession and
Community
Evolution
Succession Seers
and Climax
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AREAS OF THE LAKE
20 yrs. ago
PRESENT
LAKE
40 yrs. ago
60 yrs. ago
80 yrs. ago
100 yrs. ago
Climax (Beech-maple)
Seer (Oak-hickary)
Seer (Black oak)
Seer (Pine)
Pioneer (grass)
Bare ground (not yet invaded)
PRESENT LAKE
Figure VII.2 Evolution of a community as evidenced in the shoreline of a gradually drying lake.
volcanic eruption at Pina Tibu. A third place where at least the pioneer
and some of the early seers can be observed, are the freshly formed river
deltas such as; the delta regions of the rivers Ganga and Brahmaputra of
India and Bangladesh.
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3.7. It is also possible to simulate succession experimentally and thus
study the evolution of an ecosystem by the following method.
Thoroughly plough a piece of land then remove carefully all orgnic
matters—both plants and animals after which fence up the land. After this
the ecologist can follow up the successive stages of invasion of flora and
fauna into this piece of land. Care has to be taken however to ensure that
nothing is removed from such an experimental plot nor anything is put
into the plot from outside. It must be left alone to change on its own.
Changes in flora and fauna from one stage into another would be initiated
by the changes in the local microenvironments caused by the presence of
the earlier set of plants and animals.
3.8. Succession can even be studied by school boys and girls if they have
some knowledge and interest in biology. Here class- teachers can help.
Here is a case study. In villages in deltaic regions of Ganga often ponds
are dug. Fresh earth from the lower levels of pond are usually dumped on
a nearby suitable place. This earth is clean and has no plants or animals in
it. If a school student fences up one such a dump of fresh earth—the
dump will be an experimental plot. Now one can start observation of
succession. Soon the bare dump will be covered with one or two types of
grasses and small animals only. Then these will be gradually replaced
with shrubs and later more permanent plants. All these changes should be
carefully noted. This observation will form a good case study of
succession.
Succession can be
studied by school
students
3.9. The young ecologist should however be prepared to come accross
unexpected results. These are additional excitements of work and should
never be neglected or ignored. An observant student may discover new
facts hitherto not reported in books. Thus was discovered penicillin, by Sir
Alexander Flemming—the antibiotic which saved millions of lives. The
class-teacher of the student may be able to help him in interpreting such
findings and also in developing his power of observation. A competent
class-teacher can help in developing curiosity and hunger for knowledge
in the minds of his students.
3.10. In succession one set of plants and animals which inhabit a
particular place cause so much changes in the micro environment of that
place that, soon these plants and animals are replaced by another set of
plants and animals. Similar things happen inhuman societies as well. Here
is an example. There is a small town Birnagar, in Nadia district, West
Bengal, India, about 95 kilometers east of Kolkata. Before independence
of India in 1947, this was a sparsely populated village inhabited by poor
farmers. After independence farmers from Bangladesh migrated here and
settled down. It was still a agricultural community and in whole day only
two trains stopped near that village. Soon however Birnagar progressively
became better connected with roads and trains with other towns including
Kolkata. Its population too swelled. To-day (1998-2000) Birnagar is no
Succession in
Human Societies
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longer a village—it is a small town with municipality of its own.
Agriculturists of yesterday are being replaced by town dwellers.
Gause’s principle in
understanding
changes in human
societies
3.11. Even within the metropolis Kolkata this is happening. When Kolkata
was founded by English traders about 300 years ago, the Burrabazar area
was mostly inhabited by local business men mostly Bengalees. Soon
however smarter businessmen from outside Bengal flocked into Kolkata
and ousted most of the local businessmen. Today Burrabazar area of
Kolkata is 90% occupied by non-local businessmen and the language
prevalent in this area is not Bengali. All these social changes can be easily
understood if we consider Gause's principle (Chap VI.). Another example
from Kolkata. Soon after independence, when Kolkata was very much
overburdened with influx of refugees from Bangladesh, the then Chief
Minister of West Bengal, Dr. B.C. Roy decided to fill up a large swamp
in east of Kolkata with alluvial soil from the river Ganga and then
distribute this reclaimed land at a very cheap rate to poor middle class
Bengalees. So was the plan and so was the action. Soon something new
happened. This was not the plan. As the land prices started soaring up,
the poor middle class Bangalee land owners of Salt Lake plots succumbed
to the temptation of quick money, and by various not so straight means,
passed on these lands to rich, mostly non-Bengalee businessmen. Now
Salt Lake Bengalees are again becoming landless and are moving further
away from Kolkata. These processes are also cases of succession in
operation—succession in human societies. All these and many such
situations in human societies, past and present, are examples of Gause’s
Principle in operation. According to Gause's principle no two populations
having the same demand on the habitat (ecosystem) can live together. It
seems the earlier the social planners take cognisance of such biological
forces and plan for these as well the better it will be for us and our
children.
4. ECOLOGICAL NICHE
Definition by
Charles Elton
4.1. The term ecological niche or simply niche is a very important but
relatively new term introcuced by ecologists. Oxford ecologist Charles
Elton (1927) gave a clear meaning to this word which is now broadly
accepted. It is the “functional status of an organism in its community”.
Or, “The niche means the mode of life, and especially the mode of
feeding of an animal” (Elton—1933). It is like the profession of a person
in our society. Every person plays a definite role in a society. For instance,
a doctor plays an important role, a teacher another role, a mason still
another and so on. It is the proper functioning of all such persons and
others that keep the society working in harmony.
4.2. So is in the animal world. In a forest just as herbivores are important
so are the carnivores. For instance, in a forest the presence of sufficient
numbers of deers and rabbits etc. is a must for the survival predators like
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tigers and leopards. Again, unless the deer polulation in the forest is kept
in check by predators like tigers etc. the deer population will grow
explosively and soon the forest will be defoliated and destroyed.
Ultimately deers in a predatorless forest will face starvation and extinction.
This is exactly what happened once with Kaibab National Preserve in
U.S.A. They removed all the predators from Kaibab to promote deer
population and pleasure of tourists. The deer population grew so fast that
this almost killed the forest. So the predators have to be reintroduced for
survival of the forest as well as the deers. The presence of predators is
healthy for both the herbivores as well as the forests. (Also see 5. 2)
Similarly hawks serve a very helpful role in keeping the population of
dove and other preys healthy. Thus the scavengers like vultures and
hyenas help in keeping the forest clean of dead and decaying caracasses.
Otherwise the forests would reek with stench from carcasses. Plants also
exert similar pressures on the community.
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Kaibab Preserve:
Need of both Prey
and Predators
4.3. Thus each species in an ecosystem plays a particular and important
role in balanced functioning of the ecosystem. This role that a species
plays is the ecological niche of that species. In short, ecological niche
indicates the “profession or job” of a species in its ecosystem. Hence each
species of animals as well as plants occupies a niche in its ecosystem.
Consequently removal of a species from an ecosystem always disturbs it.
The above is a simple definition of niche, but this meaning of niche, in
the light of further studies however, has acquired more precision. So it
would be worthwhile to dwell awhile on this point.
4.4. Any species can only tolerate only a certain range of temperature and
humidity and not anything beyond it. If we take temperature and humidity
for consideration regarding the survival of a species, we shall get a twodimensional graph only (Fig. VII 3.a.). However if the species lives in a
windy place it would naturally be influenced by air current as well. So
besides temperature and humidity, air current will be another dimension of
the niche of that species (Fig. VII. 3. b.). As a matter of fact niche of a
species involves not only food but several other factors—some biotic
some abiotic. G. Evelyn Hutchinson an Yale ecologist studied various
such factors which influence the niche of a species and drew up the
conclusion that niche is an abstract n-dimensional hypervolume. This
definition however is no contradiction to that of Elton (VII. 4. 1) or, that
in VII. 4. 3. Hutchinson merely added more precision to the definition. It
seems that verily a species requires several factors—each factor within a
particular range, in order to survive, grow and reproduce and maintain
viable population in an ecosystem—i.e. its habitat.
4.5. In Nature everything has a purpose. If we come accross a
hummingbird with a thin, long and curved beak, we may wonder what
could be its purpose. In Costa Rica of South America there are some
flowers such Heliconia which are shaped like curved trumpets. There are
Ecological Niche
Hutchinson’s
concept
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Ecology for Millions
a
Cu
rre
n
t
Niche
Niche
Humidity
Humidity
Fl
ow
b
Temperature
Temperature
Figure VII.3(a and b) A two-dimensional and a three-dimensional niche.
Niche - an abstract
n-dimensional
hypervolume
some humming birds who also live in Costa Rica whose beaks are
curved exactly to fit such flowers. These flowers are pollinated by these
hummingbirds and the hummingbirds in return get their nectar from these
flowers (Fig. VII. 4.). Celebrated Charles Darwin went even further. He
predicted the presence of such a pollinator, when some botanists battled as
to how it could be pollinated, and showed Darwin a Madascaran orchid
Angraceum which secretes its nectar in the bottom of a green tubular spur
a foot long. Darwin after examining the flower, particularly its colour and
size, told that a night flying moth would be its pollinator. And lo, 40 years
later exactly such a moth was discovered which has a foot long
proboscis. Darwin's prescience was honoured by giving part of the
scientific name of the moth as forma predicta (Attenborough. Trials of
Life, 1990, p. 65).
Some occupants of
various niches and
the roles they play
4.6. If we patiently examine living beings and find out how and where
they live, we shall realise that in Nature nothing is a waste. In her master
plan Mother Nature has a job and place for every living being. All fit into
their respective niches. It is we human beings out of our insatiable greed
coupled with ignorance, ‘throw a spanner’, now and then, into her this
otherwise perfect machine and thus put it out of balance. This is what is
colloqually known as disturbing the ecosystem or upsettig the ecobalance.
Some people out of excess of sentiment and lack of ecological concepts
try to save all the cats and dogs they come about. This is a mistake.
Regular culling is a must to keep these populations healthy and the
ecosystem balanced.
4.7. Three Indian carps beautifully illustrates how each species fits the
niche it occupies. In east Indian ponds there are three common carps.
These are Labeo catla, Labeo rohita and Labeo calbasu. Overall these all
stay in the same ecosystem namely ponds. But Labeo catla feeds on the
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159
Figure VII.4 A Hummingbird visiting a flower.
surface planktons, L. rohita feeds upon the planktons in the middle depths
of the pond while L. calbasu feeds only upon the dead and decaying
organic mater settled in the bottom of the ponds. So there is no
competition between them as they occupy different niches of the same
ecosystem i.e. the pond. Because of difference in food habits these carps
differ in their facial features as well. L. catla has a wide mouth and
L. rohita's mouth opening is narrow but the mouth opening of L. calbasu
is subterminal i.e. opens downwards and has short barbels guarding the
rim of the mouth. These barbels help in search of food at the bottom of
the pond where light is scanty. These bottom feeding calbasus play the
important role of recycling the organic nutrients which would have
otherwise remained locked up in detritus in the bottom layer of the pond
and thus unavailable for recycling into bio-geo cycle of chemicals for a
very long time.
4.8. This special role played by a species in ecosystem is its niche. In
simple analogy one can compare the niche of an animal living in an
ecosystem, with the exact address of a person as the niche and the postal
pin code as the ecosystem.
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5. BALANCE IN COMMUNITY
Disturbances in
Community Balance
5.1. In a balanced and stable community that is climax community, each
species has a specific and important role to play. These roles are the
niches these are occupying. Let us compare this with a large human
family. Here somebody might be only earning, somebody cooking,
somebody maintaining the house, somebody tending the children and so
on. In such a balanced family if somebody stops doing his or her duty
properly, the whole family would be thrown out of gear. This is exactly
what happens if suddenly in a stable community (climax) a species is
removed or a new species is introduced. Here are some example.
Kaibab plateau:
Prey-Predator
balance
5.2. The Kaibab plateau of Arizona, U.S.A. has an area of more than half
million acres. Prior to 1907 it had good populations of deers, wolves and
pumas. It was a stable community. At that time there were about 4000
deers. But between 1907 and 1923 most of the predators were deliberately
removed. Within this short period the deer population being free from
predator pressure, exploded to about 100000, almost decimating the forest
through overgrazing. Consequently deer population crashed and the forest
became poor. Subsequently the forest department had to reintroduce
predators establishing a much smaller but sustainable deer population in
Kaibab (see also art 4. 2). This is a vivid example of what may happen if
all on a sudden a species is removed from an ecosystem. From this the
dove-lovers and hawk-haters may rethink about hawks and decide if
hawks are really so bad after all.
Introduction of a
Species: WaterHyacinth in India
and Bangladesh
Cactus in Australia
5.3. The water hyacinth which is today most common in ponds and rivers
of India and Bangladesh, is a native of South America. It is said that some
European lady, to decorate her garden-pond brought it from South
America to India. Oh what a havoc it has created ! It disrupted the entire
fresh-water community. It has choked the canals and ponds, encouraged
malaria which has become an everlasting epidemic and spawned many
other human miseries in the entire eastern India and whole of Bangladesh.
Really this has been a calamity. Indians and Bangladeshis still do not have
any effective solution to water hyacinth problem.
5.4. Here is another example. This is different from the above in the sense
that here they could find a solution. The cactus Opuntia was taken by a
British coloniser from India to Australia to decorate his garden. In no time
it jumped over the fence and covered hundreds and thousands of acres of
grasslands spoiling valuable pastures. Fortunately, after lots of efforts
though, Australian entomologists could find in India a moth Cactoblastis
cactorum which keeps the Opuntia in check in its in its native land. When
introduced into Australia Cactoblastis cactorum soon brought down
Opuntia infestation to a managable level, much to the relief of the pasture
owners. There are more such examples.
5.5. All species belonging to a community are, in some way or other,
connected to each other. Right from the imperial tigers to the lowly and
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shy earthworms, all play important roles in the game of life. While the
roles of tigers may be easily understandable to most of us but that of
earthworms requires unbiassed and discerning eyes. Let us spend some
time on this. Tigers (Panthera tigris) are carnivores which depend only
upon meat as food. Depending upon its size a tiger needs 10-15 kg. of
meat a day. Deers, hogs, porcupines etc. are its main food. So a tiger kills
lots of animals for food. It has been estimated that nearly 30-40 square
miles or forest area is required to provide a single tiger with food ( Col.
Keshri Singh, Jaico, Bombay, 1967).
161
Prey-Predator
relationship: Tigers
and Deers
One may think it is a waste to allot so much of forest area for a single
tiger. But tigers and similar predators are very useful for the health of a
forest. Without the presence of a powerful predator like tiger, the prey
population such as deers will soon outgrow the capacity of a forest and
destroy it by defoliating the trees and nibbling away the barks. Secondly,
a predator usually predates upon the old and the weak and the young
ones. Thus the predator helps to keep the prey population healthy and
their number in check. Besides these the imperial majesty a tiger imparts
to its forest is surely undeniable. Tigers are also great tourist attraction
and have potential for good revenue.
5.6. Now let us examine the shy and self-effacing earthworm. Pheretima
posthuma is a common Indian earthworm. These are small ( 8"-12" long)
backboneless (INVERTEBRATES), tubular, legless and blind creatures
belonging to the phylum Annelida. Their bodies are made of a series of
rings with mouth and anus situated at the two extrimities of the body tube.
They are nocturnal and live in forest floors or agricultural fields where
one may occasionally come accross these crawling about upon moist
earth. Usually earthworms’ presence is indicated through earthworm
mounds. Prior to 1850’s biologists did not think that earthworms play an
important role in the economy of forests. It took the genius of Charles
Darwin to understand the important role that earthworms play in
ecosystem. Darwin published a monograph on earthworms (The
Formation of vegetable Mould throuch the Action of Worms. C. Darwin.
1888. John Murray. London), which is still a masterpiece. Earthworms
live in tunnels, dug by these, within soil. Earthworms are vitally important
for the health of forest and agriculture. They live on dead and decaying
vegetable matter and thus break down leaves etc. which cover the forest
floor. In this way earthworms hasten the return of organic matters to soil
so that these can be reused by plants for biosynthesis. The earthworms
also play a significant role in turning over soil by making mounds, ouside
their burrows, of soil which has passed through their alimentary canals
(Fig. VII. 5.). Today earthworms are considered so useful that, many
farmers deliberately bring and put earthworms in their fields and gardens.
5.7. The snakes are another member of community which have suffered
very much through us due to our misconception about them. Bible has
Detritus feeders:
Earthworm
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Ecology for Millions
Earthworm
Mounds with air holes on top
A fern with three
fronds
Air Holes
Soil
surface
Earthworm
Two earthworm
tunnels on
mounds on top
Soil
Figure VII.5 The mounds of earthworms.
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depicted snakes as representative of Satan which it certainly is not. It is
a predator and lives on small animals—such as insects, rats, birds and
frogs. As the main terminator of field-rats snakes help the agriculturists.
Like tigers as predators, snakes too keep their prey in check and thus
help to maintain the ecosystem in balance. General public in most places
have a tremendous fear of snakes as bite of some snakes can be lethal,
so they try to kill them, one and all, whenever they can. In this way we
not only do injustice to snakes but also upset the local eco-balance. Most
snakes are harmless and shy, even cobras avoid encounter with human
beings. It seems save African mamba no snake attacks unprovoked or
unless threatened. None should kill snakes unless it is a must. Just
because a few snakes can kill us by their bites we try to kill them all. It
is very unfair. Just as we have, snakes too have their right to live. We
ecologists think that unless it is a must a snake, whatever the species,
should never be killed. Snakes are firends and not foes. They eat rats and
thus directly help the farmers. Also unless threatened they do not bite.
5.8. Here are some of my own experiencec. At Pilani, Rajasthan, India,
where I spent most of my academic career, once I came upon a large
cobra (Naja naja) about 5' or so, busking in sun. Without noticing it
when I walked to about 8' of it, it raised its head and spread the hood.
Then I noticed it. I believe it was afraid and felt cornered—so in
desperation threatened me. I stopped then and there and watched it.
When it felt I am not going to attack it, it felt assured. Then slowly it
moved away and I moved on. Another cobra, this one a young one, used
to come, now and then, into the courtyard of our house, presumably
trailing some rats. It never tried to attack us nor we harmed it.
5.9. A large, balanced and self-sustaining ecosystem consists of a climax
community and its abiotic environment. The functioning of the community
of such an ecosystem is comparable with the orderly functioning of
household. Here every member has a definite role to play. Similarly each
species in a balanced ecosystem, is important. Each has a role to play.
5.10. Earlier we have seen that the consequences of interactions between
two species may be + ve, – ve or 0 (i.e. neutral). So also are the nature of
the various ongoing biodynamic processes within the community of an
ecosystem. Looked from one angle one discrete biodynamic process may
appear + ve and another – ve but when we take a totalistic view of the
function of the entire community we find that collectively i.e. in sum total,
all interactions lead to the sustenance of the health of a natural community.
6. APPROACHES TO COMMUNITY STUDY
6.1. Very often people use the term totalistic in their discussions.
Ecologists use two other words—holistic and meristic. Holistic means
looking at the whole complex of things that constitutes an ecosystem or
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The Friendly
Snakes
My experiences of
snakes
Biodynamic forces
and Eco-balance
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Holistic and Meristic
views: Are they
different?
Ecology for Millions
the community or similar interconnected assembly of things. Here are two
simple examples. Suppose we have a small undisturbed forest valley as a
self sustaining ecosystem along with a rivulet which origins and flows out
of the forest then, by examining the water of this rivulet at regular
intervals we can arrive at a pretty good picture about the health and nature
of this ecosystem. This is a holistic study. Similarly, if we monitor
carefully the inputs into a town i.e. the merchandise that goes into it for
sell, we can make a pretty good idea about the financial capability and
social tastes of the people who live in that town. This is also a holistic
approach. But in meristic approach an ecologist would rather take one
species i.e. a population and try to work out in details the various aspects
of its biology—such as energy requirement, nature of food consumed,
breeding habits, territoriality etc. Such detailed study on one single species
may take the whole life of a biologist. Jane Goodal (1980). Spent her life
studying primates of Africa and Karl Von Frisch spent his life studying
bees in Germany (The Dancing Bees. An Account of the Life and Senses
of Honey Bees. Methwn and Co. London. 1954). Still the significance of
their findings went far beyond primates or bees. Their data helped
enormously in holistic studies—Goodal’s in understanding the behaviour
and evolution of all primates and Frisch’s in understanding the mechanism
of foraging and pathfinding of bees and many other insects. Charles
Darwin was a pioneer biologist who simultaneously used meristic studies
and holistic approach to interpret biological processes. Thus he reaped
ample harvest and presented the world, along with Alfred Russel
Wallance, the single most important work in biology in ninteenth
century—mechanism of origin of species (1859). Therefore holistic and
meristic approaches are complimentary to each other. A synthesis of both
yields maximum information in understanding the processes of life. In a
community every single species is connected with heavy other species
however remotely they may appear to be so.
7. SPACE AND CARRYING CAPACITY
Here let us repeat some of the basic terms used so far.
(1) AUTOTROPHS : Green plants. They are also called Primary
Producers and the symbol is ..........P1.
(2) HETEROTROPHS : Animals of all types. Those which are
herbivores are called Secondary Producers and the symbol is
..........P2.
Those which are carnivores are called Tertiary Producers and
the symbol is ..........P3.
Those which are parasites are called Quaternary Producers and
the symbol is ............P4.
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(3) SAPROTROPHS : Bacteria and Fungi. Those which feed on dead
organisms—plants and animals and the symbol is ........S.
Saprotrophs are the ones which break down and decompose any and
all producers—P 1 , P 2 , P 3 , and P 4 , after their death and release the
nutrients locked into their bodies back to abiotic environment for
recycling. As these absorb nutrients at liquid state only, these are named
sap-feeders or Saprotrophs.
7.1. Therefore Plants (P1), Herbivores (P 2), Carnivores (P3 and P4) and
Bacteria and Fungi (S) are present in all self-sustaining ecosystems. These
sustain the ecosystem and are in turn sustained by the ecosystem. Hence
P1, P2, P3, P4, and S are the fundamental biotic components of any healthy
ecosystem. Removal of any of these, would throw the ecosystem out of
gear (Chap. II.)
7.2. Now let us examine how much land is required by a herbivore and a
carnivore. Generally weight by weight, a carnivore requires 50 to 100 times
of land that a herbivore requires. This would be obvious if we check the
amounts of biomass of animals of various trophic levels which are
supported by one acre of forest land (Figs. VI. 8 and 6). From these one
can easily understand that the supportive capacity of land or a forest for an
Figure VII.6 Cave paintings of Altamira—a dying bison.
Land Requirements
of Heterotrophs
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Ecology for Millions
animal depends upon how far away the animal is from the primary
producers (P1) i.e. the plants. So Land can support more herbivores than
primary carnivores (C1) and more primary carnivores than secondary
carnivores (C2). That is why a tiger in land or shark in sea both of which
are top carnivores, require huge areas to support them. Estimated
requirement of forest land, depending upon the nature of forest, to support
one tiger varies from 30 to 40 square miles. For shark however we do not
have any definite data but, it seems being top carnivore a shark too would
need lot of sea area to support it. Sundarban forest in the Ganga delta of
West Bengal, has an area around 2585 square miles. So it can support only
about 85 tigers. Whether such a small number of tigers form a genetically
viable population is not quite clear. We believe, our planners, as a thumb
rule, should always provides for at least 250 numbers of any species of
large size as a viable and genetically healthy population. Owing to poor
planning and greed of unscrupulous people India’s majestic tigers Panthera
tigris and grand one horned rhinos Rhinoceros unicornis are almost at the
brink of extinction. It would be a black day for Indians and India's
ecosystems if these lovely and majestic animals are gone.
Over-populated
Countries
7.3. From the above figures and Table VI. 6 one can work out
approximately, depending upon food habits and size, how much space an
animal may require. Another lesson that can be drawn from this figure is
also vary crucial. Same area of land can support more herbivores than
carnivores. Therefore for overpopulated countries like Gaza Strip (2744 p.
sq. km.), Bangladesh (870 p.sq. km.), Japan (332 p.sq. km.) and India
(299 p. sq. km.), vegetarianism would be less eco-taxing (refer Table no.
VI. 6 of Chap. VI). It appears to maintain an healthy environment all
countries should aim to keep their population densities within a target aim
of 100 to 200 p.sq. km. This number however may vary somewhat
according to the rate of primary productivity of the ecosystem
concerned. For instance 200 p.sq. km. for a desert is too high and too
low for a tropical rain forest respectively. Here ecologists can help the
planners. (Also it is now established in ethology that availability of open
space helps healthy growth of human minds).
Production Efficiency
7.4. The basis of the above statement is related with a concept called
production efficiency. Production Efficiency (PE) is the percentage of
the food that is assimilated by a producer (A1) to that which is converted
into new biomass of the producers (P1) and efficiency as (E1)
Production Efficiency or PE =
P1
(when expressed as percentage)
E1
Generally invertebrates have a rather high production efficiency (30-40%),
cold blooded vertebrates (10% or so, and warm blooded vertebrates
including humans have a PE of only 2—5% or 20: 1 or so. This means
warm blooded carnivores make a much higher demand on the food
resources of the ecosystem they live in than the cold blooded imertebrates.
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(Some require evenmore. For example, hummingbirds who are nectar
feeders, require nectar about 50% of their body weight per day).
7.5. Human beings are also animals—warm blooded animals
(endotherms). But being exceptionally intelligent animals, who can think,
learn and plan, their conversion ratio of 20 : 1 could not contain their
ascendancy over all other living beings within a very short time. (Dr. J.
Bronowski has given a very captivating account of this in his book—The
Ascent of Man, 1973, B.B.C.)
Culture and Land
Requirement for
human beings
There are two reasons for this.
(i) They can manipulate their environments end, depending upon their
culture, get more out of the same land than other animals,
(ii) Their requirements are not mere food—depending upon the
“quality of life” they aspire for, men of to-day not only need
much more land but many other items to sustain them than other
animals of comparable weights and food habits. Because of these
two extra-ordinary qualities human beings to-day are posing a
serious threat to the stability and health of all ecosystems of the
entire world.
7.6. When English farmers introduced sheep in Tasmania, their number
rose rapidly with time till, the number reached a level of density beyond
which it could not be sustained profitably (Fig. VI. 6). Apparently that is
the carrying capacity of Tasmanian pastures for sheep. Bus this would not
work for human beings—Homo sapiens.
7.7. Human populations rose very very slowly during the early phases of
human culture. In recent ages however the populations rose very fast
(Fig. I.1 and III. 18). This rise is linked with the food procurement
systems developed by people of different cultures. From the beginning of
civilisation till now, human societies have passed through three successive
distinct phases of cultures and now is poised at the doorstep of another.
These cultures and their characters are as follows (Also, improvement in
medical facilities contributed heavily in population rise).
8. PHASES OF HUMAN CIVILISATION
8.1. First was the Hunting Phase. This is the earliest and pre-historic
phase of human civilisation. People used to live in small groups or clans
wandering about from place to place, living off from land and water mainly
by hunting animals and eating whatever wild fruits, fishes and roots they
could gather. In this way whenever the food supply of an area would get
depleted, they would move on to another. These hunters did not have any
written language but some of them developed superb painting and sculpting
skills. The cave painting of hunting scenes at Altamira, Spain are examples
of their superb talents. These cave painters of Altamira certainly achieved
the acme of the hunting phase of human culture (Fig. VII 6).
1. The Hunting
Phase
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8.2. The hunting era ended about 10—8000 years ago. There are a few
scattered tribes who still live by hunting. Some of these are Bushmen of
Australia, Jarwas of Andaman Islands and a few scattered tribes. World's
human population was very low at that time. The best estimate seems to
be less than 5 million (Ehrlich and Ehrlich, 1970. p.6) as, it required a lot
of land to support a hunting tribe who would produce nothing but live off
the natural produce of land. Also population growth was very very slow
because many people died before reaching mature age owing to hunting
accidents, diseases, starvation and inter-clan fights for mates and hunting
grounds. Life was a never-ending struggle with no holiday.
2. The Pastoral
Phase
8.3. Next came the Pastoral Phase. During this phase men learned the
technique of domesticating animals. Cows, horses and dogs were
domesticated and bred. These domesticated animals provided an yearround assured supply of food and clothing (from animal hides). With
food and clothing assured, human population saw a faster rate of growth
(Fig. III. 18). Such people whose life depended on domesticated animals
are called pastoral people and their culture-pastoral culture.
8.4. Pastoral people have given humanity two great religions—Judaism and
Christianity and one great—perhaps the greatest military genius the world
has ever seen—Chenghis Khan. Alone he conquered, with his mounted
archers, land spread from Mongolia in the east to Persia in the west
(Genghis Khan : Emperor of All Men, Harold Lamb, Bantam Books, New
York, 1957). Never in human history such a superb military genius has
been seen—before or since . Pastoral people are still found in scattered
pockets of the earth. Most notable of them are the herdsmen of Mongolia.
Besides these people still migrate from place to place along with their herds
of cattle and horses and their yarts (collapsible tents of felt). Besides there
are Bedouins of Arabia who still live live off herds of camel and stay in
tents and the Lapps who are Reindeer herders of Northern Sweden. During
pastoral phase, because food supply was more assured and steady,
humanity saw a spurt of rise in population (Fig. III. 18).
3. The Agricultural
Phase
8.5. The phase which is present phase is the Agricultural Phase. Soon
after the rise of pastoral culture, in different pockets of the world, rose
the next phase in evolution of human culture—the agriculture phase.
People noticed that seeds of some grass are eatable—so they tried to
cultivate these. Soon in Africa and Asia they learnt how to cultivate
wheat, rice, millet etc. In South America they cultivated maize.
Agriculture gave two things—settled life and more food. From
agriculturists rose some of the most remarkable civilisations—one of them
is Egyptian. This is the civilisation which flowered upon the valley of
Nile river of Africa—the civilisation of Pharaohs—from around 5000 to
3000 B.C. The awe inspiring pyramids of Giza, Egypt and the stone
carvings of Luxor and Abu Simbel also of Egypt, still bear silent witness
of the glory and grandeur of that age (VII. 7).
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Figure VII.7 One of the stone carvings of Luxor—a Pharaoh.
8.6. Besides, pyramids, Egyptian culture gave us hieroglyph (picture
writing) and a very advanced agricultural civilisation which spread far and
wide such as in valley of river Indus, Pakistan. There we find evidences
of planned city life with underground sewage canals etc. From other
agricultural civilisations such as in the valley of the river Ganga, India, we
got a most beautiful and thought-provoking philosophy of life, the Vedic
philosophy. The valley between the rivers Euphrates and Tigris, Iraq, gave
us another powerful culture which produced besides great kingdoms
beautiful stone carvings and the valley of Yangtze Kiang, China, gave us
another remarkable way of life—Taoism. The Egyptians migrated to and
spawned the early civilisations of South America. These are only a few
of the vast cultural, scientific and architectural outpourings of agricultural
societies. It is still flowering. But let us stop here. Our theme is ecology.
8.7. The agricultural life is a settled life and assured supply of food, gave
a further boost in the rise of human population (Table-VII. 1 and Fig.
VII. 8). These three successive cultural phases of human development
increased the productivity of land and thus its carrying capacity (for
Cultural Phase and
Boost in Population
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Ecology for Millions
Table VII.1.
CULTURES AND RISE IN HUMAN POPULATION DURING THE LAST TEN THOUSAND YEARS.
EACH CHANGE IN CULTURE AND ADVANCE IN KNOWLEDGE IS ALWAYS FOLLOWED BY AN
INCREASE IN THE RATE OF POPULATION GROWTH
Period BC/AD
Population (In millions)
2000 AD
6000
1000 AD
00 AD
1000 BC
2000 BC
3000 BC
4000 BC
5000 BC
6000 BC
7000 BC
8000 BC
900
700
500
400
300
200
175
150
125
100
}
}
}
Civilization, methods of food gathering and other factors
Agriculturists; Industrialists, use of Modern Medicine to reduce
pre-reproductive deaths and discovery and occupation of huge
continents – Americas and Australia
Agriculturists and Pastorals
Agriculturists and Pastorals
Agriculturists and Pastorals
Agriculturiests, Pastorals and Hunters
Agriculturists, Pastorals and Hunters
Agriculturists, Pastorals and Hunters
Agriculturists Pastorals and Hunters
Hunters and Pastorals
Hunters and Food gatherers
Hunters and Food gathersrs
human beings) by approximately 10 times in each phase. For instance, if
100 acres of land could support only 1 hunter, the same would support
10 pastorals or 100 agriculturists. Thus the carrying capacity of land, for
human beings, is very dependant upon the technology people employ to
obtain food from their ecosystems.
Effect of Industrial
Revolution on
Agriculture
8.8. In the later eras of agricultural phase, particularly industrial revolution
in Europe (16th century onwards ), men acquired new innovative tools
for agriculture. These are mainly, machine ploughs, harvesting machines
and chemical fertilisers. These artificial energy inputs to agriculture gave
a further boost to cultural growth as well as numerical growth of human
beings. People also had time to think and innovative. Consequently
agricultural production went up even further. In to-day’s world the
agricultural productivity of land and economic clout of a country is very
much linked with the level of technology the agriculturists there employ
(Table. VII. 1).
8.9. Simultaneously growth in our knowledge of horticulture and animal
husbandry, has contributed substantially to achieve all these. As a matter
of fact five species of plants played a significant role to change the face
of earth. These are :
(i) Quinine—a bitter alkaloid obtained from the bark of Cinchona
tree, which cures malaria and thus helps human population
growth.
(ii) Sugar—a very sweet chemical obtained from the sap of a tall
grass Saccharum officinarum.
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171
5
(Mostly due to advances in medical science
which stalled natural compitition elimination)
Agriculture & Industery (growth rate 1.4 %)
4
12,000
Agriculturists (growth rate 0.1 %)
1
Pastorals (growth rate 0.03 %)
Population (billions)
2
Hunters (growth rate 0.0001 %)
3
10,000
8,000
6,000
Years: B.P. (before present)
4,000
2,000
Today
Figure VII.8 Growth rate of human population over the last 12,000 years.
(iii) Tea—a mild stimulant obtained by processing the bud and young
leaves of a shrub Thea sinensis.
(iv) Cotton—white downy fibres obtained from the seed pods of
shrub of Gossypium sp.
(v) Potato—white edible underground tubers of a small plant
Solanum tuberosum.
Henry Hobhouses’s account of all these is very attractive (SEEDS OF
CHANGE : Five plants that transformed mankind. PAPERMAC. 1992).
8.10. Carrying capacity of land for human beings therefore, depends upon
the techniques men employ to extract food from land. Now population
growth is being boosted by two factors—first, by obtaining more food
from same land and secondly, by reducing child-mortality through better
medical care. The resultant explosive growth in population is now posing
Explosive Growth of
Human Population
and Survival of
Ecosystems
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Ecology for Millions
a severe threat to the very survival of our ecosystems. To-day we are 6
billions, hurtling towards 9! We are just too many for Mother Earth to
hold. This must be halted.
The Silver Lining
8.11. Still there seems to appear a silver lining in the horizon. Human
beings today are at the threshold of another techno-cultural phase—the
Phase of Genetic Engineering and Information Highway. These two
powerful tools will enable human beings to increase the production of
food manyfold—perhaps ten fold once again. Simultaneously through
vigorous family planning even more will be achieved. But like Aldus
Huxley’s interesting book “Brave New World” that road may not be ‘roses
roses all the way’ More about these in Chapter X.
This page
intentionally left
blank
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175
CHAPTER VIII
BIOMES
(The Nature In Her Splendours)
Nature abhors vacuum. Unless a place is absolutely uninhabitable, each
and every corner of this biosphere is colonised by living beings. We shall
begin this chapter by quoting from three extraordinary persons—one a
poet, another a philosopher and the third one a naturalist, all praising and
wondering at marvels of Nature.
The Indian poet Rabindra Nath Tagore wrote—
The American philosopher Henry David Thoreau wrote—“I went to
the woods because I wished to deliberately, to front only the essential
facts of life, and see if I could not learn what it had to teach, and not,
when I came to die, discover that I had not lived.”
This is what Alan Moorehead wrote about Charles Darwin’s ecstatic
reactions to Brazil’s rainforest which he visited in 1832. “They (i.e.
Darwin and his companions) were a party of seven, all mounted on
horseback, ........... they followed the coast for the first few days and then
turned inland into the tropical rainforest................................he was
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Ecology for Millions
enthralled, enraptured. All around them vast ceiba trees and cabbage
palms, as slender and tall as ships’ masts,............... From the topmost
branches Spanish mosses and long rope-like lianas trailed down through
the green light ............ incredibly brilliant birds : the toucans (Rampastos
toco) and the green parrots................ The blood curding cry of the howler
monkey erupted through the silence .................”.
Who has not shivered in pleasure and excitement at the first sight of
the georgeous beauty of the snow clad Himalayas ? Whose soul has not
been lifted at seeing the breaking out of sun through the crests of ocean
waves or, who is not charmed at the resplendent fall-veil of the Blue
Ridge Mountains of U.S.A.? Photo VIII.1. Or think of the awe inspiring
sight of Niagra Falls where every second 800,000 gallons of water is
hurtling down from a rock ledge forming an arc of half a mile. Such and
many more are the bounties of our universal mother—MOTHER EARTH.
Our Earth is so variegated, so beautiful and so bountiful that, if we
handle her with a little bit of care and love, she will ever remain a source
of endless beauty and bounty to us all. It is time we address ourselves to
this noble and urgent task. This chapter will be devoted to presenting a
brief account of the varieties of our ecosystems and the following chapter
on how we are damaging these precious ecosystems and the chapter
after next i.e. the last chapter of this book on how we can rectify our
mistakes and blunders before it is too late.
Main Ecosystems of
Earth
From the ecologists point of view the main ecosystems of the
earth can be broadly grouped into land and water ecosystems or
Biomes with sub-divisions in each of them according to their dominant
physical and biological features. Here is a table enlisting the main biomes
of the world (Table VIII. 1.).
Each of these biomes pose their distinctive environmental challenges
which lead to various adaptations. However even a mere enlistment of the
challenges and adaptive responses of living beings of those, will occupy
too much of space and time. Besides this is not the aim of this simple
book. We shall therefore try to confine ourselves to the most salient
features of these biomes and a few striking examples of adaptations. (The
recent trilogy by David Attenborough—Life on Earth 1979, The Living
Planet 1984 and The Trials of Life 1990, published by Little, Brown and
Company, has beautifully presented some of these themes). Here is a
world map indicating broadly the locations of the principal biomes
(Map II. 1).
1. AQUATIC BIOMES
These are ecosystems where the environment is predominantly water.
Naturally these ecosystems are of considerable variety. Here are the main
ones.
Principal Biomes
Aquatic
(1) Swamps (Fresh water) →
(2) Lakes and ponds
(Fresh water)
(3) Streams and rivers
(Fresh water)
(4) Estuaries or Deltas
(Brackish water)
(5) Caral Reefs (saline
water)
Terrestrial
(1) Tropical Rain Forests →
Shallow waters
on large areas
→ Permanent land
locked body of
water
→ Running water
systems
Mostly in warm areas
and some in Siberia
All over the world
All rivers and streams
(3) Temperate Deciduous →
Forests
→
Where rivers
meet the seas
Reefs formed
of layers of
dead shells of
small sea
anemones
Shallow (200 m.)
areas of seas
fringing all
continents
Vast expenses
of open seas
Mouth of Amazon,
Ganga etc.
In continental shelves
in tropical and subtropical areas
(4) Boreal Forest
→
(5) Scrubland
→
Shores of all
continents
(6) Savanna
→
Wide expanse of
grasslands scattered
with a few trees
All oceans
(7) Tundra
→
Special areas
of seas where
ocean currents
push up some
of rich
sediments
A few special areas
(8) Desert
→
Sub-arctic areas
with seasonal
grasslands
Mostly covered
with sanddune
with no or
sparse rainfall.
→
(6) Continental shelf
(saline water)
→
(7) Open ocean
(saline water)
→
(8) Upwelling zones
(saline water)
→
(2) Temperate Evergreen →
Forests
Humid, dark and
dense forests
Forest with Broad
leaf and evergreen
trees
Deciduous forests
where leaves fall
off in winter
Cold temperate
regions with
conifers
Semi-arid areas
with thorny plants
and shrubs
Mostly in some
tropical water-sheds
Mostly in cold
temperate regions
Pre-arctic areas
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Table VIII.1 Main Biomes of the World
177
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Ecology for Millions
1.1 Swamps or Freshwater Wetlands
Swamps or Freshwater Wetlands
a. Whereever a considerable body of water accumulate over a large area
in modest depth, it forms a swamp or a wet land. Such swamps are
mostly associated with fringes of lakes as with African rivers or in rivers
in Amazon valley or river Ganga of India. The swamps in Florida, and
Eastern part of Kolkata, India, are now-a-days very much talked about.
We shall come to these later. Generally swamps enjoy heavy rainfall (100"
or more) and warm climate (20—25°C). These wetlands are mostly
situated in the warm parts of the globe i.e. from the tropics to about 40°
North and 40° South latitudes (except the swamps in northen Siberia). So
the climate is rather warm—around 18/20 to 20/25°C, humid and with
plenty of rooted plants. Also the bottom of swamps are rather muddy and
silty.
Flora and Fauna
b. The flora and fauna of swamps have characteristic features. As the
water is nutrient rich, nearly stagnant and shallow such wetlands
encourage growth of rooted plants, giant water lily such as the lilies with
leaves about 1.8 m. long in Amazon swamps and the beautiful floating
lake-gardens of Dal Lake in Kashmir. Water hyacinth is another plant very
common in wetlands all over the world (Fig. VIII. 2.).
Float
Fig. VIII.2 A clump of water hyacinths.
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Fauna of wetlands too, like flora, have some characteristic features.
They are generally suited to highly humid and warm climate and home of
some large aquatic animals such as Anacondas (a species of water
python), Crocodiles and Alligators of Americas, Hippopotamus in Africa.
This is because in water body weight becomes much lighter (owing to
buoyancy). The anacondas of South America may become as long as 10
meters weighing 230 kg. or so ; the crocodiles may becomes as big as
7—8 meters and hippo may weigh 2.5 tons and consume 175 Kg. of
aquatic plants and grasses daily. Naturally these large animals' faecal
matters add a lot of nutrients to the swamps. Besides, nutrients are
further added along with the run off of water from the watershed of the
swamps. Hence the fast silting is a conspicuous feature of most swamps.
The silted up rims of swamps gradually get occupied with lowland forests.
Swamp Adaptations
c. The birds of swamps usually have long legs and splayed feet to facilitate
walking in shallow waters and muddy surface. In some swamps of
South America, Afrika and Australia, which dry up seasonally every year,
three species of fishes have developed accessory respiratory organs in the
form of lungs—to enable them to breath in air and thus tide over the dry
season (Fig. III. 9 and Fig. VIII. 3).
(a) Longitudinal section
(b) Transverse section
Oesophagus
Swim bladder showing the
alveoli of lungs
Fig. VIII.3 The lung of a lung fish–Protopterus sp.
1.2 Ponds and Lakes
a. A lake is a permanent land-locked body of water whose water supply
may be maintained either by the aquifers (water-bearing strata of soil) or,
run-off from the watershed during monsoons or, through rivers which
open into this or both. A pond is an artificial impoundment of water made
by men to serve their needs. Naturally being manmade, ponds or
impoundments are small in size, Recent river-dams however have created
huge artificial impoundments.
Ponds and Lakes
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b. The main abiotic component of lakes is water or rather excess of it.
Water though vital for life, poses challenges if it becomes more than
necessary. Every living being must have water in their tissue but only in
a particular proportion. Deficit or surplus of water both pose problems.
Animals get rid of excess water either through urine or perspiration or
both (in rare cases such as tears of crocodiles and saliva of dogs serve
the same purpose). Where and when water is insufficient animals move
away from such places but plants which are stationery develop special
dessiccation resisting features like converting leaves into thorms or
developing thick barks etc. That is why semi-arid places have mostly
thorny plants like cactus etc. When water is in temporary short supply,
plants wilt i.e. the stomatal openings* of the leaves narrows as the
stomatal cells become flaccid, so the leaves sag down. This helps in
reducing the loss of water-vapour through leaves.
Lentic and Lotic
habitats
c. Let us now come back to lakes. Before going into details of lake
ecosystems the understanding of two terms are necessary. These are Lentic
and Lotic. Lentic means standing water habitats such as swamps, ponds
and lakes. Lotic means running water habitats such as springs and rivers.
Problem of surplus
water for freshwater
beings
d. Animals and plants in lakes have no shortage of water; in fact it is
excess of this they have to deal with. As the body fluids of animals is
more concentrated (hypertonic) than the surrounding water (hypotonic),
water always tend to enter the bodies of the animals. The fresh water
animals get rid of this excess water by producing plenty of urine (which
is hypotonic).
Vertical Zonations
in lakes
e. Waters of lakes which are deep—20 metres or more, have two types
of zonations—one according to light penetration and the other according
to thermal stratification. The upper layer where light penetrates is known
as Photic zone and the lower layer where the light does not penetrate is
called Prefundal zone. The photic again has two sub zones. Shore areas
where light penetrates easily and have rooted plants is called “Littoral
zone”. The area next to this where light penetrates but the zone is too
deep for plants to strike roots is called “Limnetic Zone”. Fig. VIII. 4. As
the photosynthetic activity is likely to be progressively less as one goes
deeper, one should note depth of the place when he/she takes a sample
of lake water to measure productivity.
f. Besides the above photosynthetic stratifications, lakes which are deep
enough (20 metres or more) show thermal stratification in their waters.
In a lake in temperate region during summer as the water is warm, it will
form the top layer and the cold heavy water will stay in the bottom. There
*Stomatal openings (from stomata, pl. of stoma). Minute openings on the under
surface of the leaves, in between two guard cells, regulating diffusion of gases into and
out of the leaves for respiration.
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Biomes
181
SUN
Littoral
zone
Limnetic zone
I. Littoral
zone
(zone of rooted
plants)
Profundal zone
II. Limnetic zone
(zone of
phytoplantktons)
III.III.Profundal
Profundalzone
zone
(zone
of no
(zone
of
photosignthetic
photosignthetic
activity)
activity)
Fig. VIII.4 Vertical zonations of a Lake.
will be no mixing between the two. The top warm layer is Epilimnion,
the bottom cold layer is Hypolimnion and the intermediate layer is
Thermocline (Fig. VIII. 5.). As there is no photosynthetic activity in the
cold heavy water of the hypolimnion so gradually this zone becomes the
repository of nutrients.
Thermal Stratification of a Lake
Lake surface
Epilimnion
(top water: lighted &
high photosynthetic
activity)
Depth 20 m
22°C
21°C
Thermocline
10°C
8°C
5°C
Hypolimnion
(bottom water: cold &
heavy-no photosynthesis)
Fig. VIII.5 Thermal stratifications of a Lake.
g. As the winter approaches (in colder climates) the temperature of the
upper water cools down. When it touches 4°C (i.e. when the water is
heaviest) the upper cold and heavy water sinks to the bottom and the
lower warmer and lighter water rises up. This is fall overturn. This
bottom water which now comes up is however loaded with nutrients.
Soon with further drop of temperature the surface water of the lake
freezes and covers the lake as a hard protective coat. No further
movement of water takes place. In spring when the ice melts there is a
Fall Overturn and
Plankton Bloom
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Ecology for Millions
Plankton density
sudden spurt of plankton multiplication in the epilimnion—as now the
water is loaded with nutrients and the temperature is favourable. So there
is an explosive multiplication of planktons. This is known as plankton
bloom (Fig. VIII. 6.). Just like a bloom as soon as the nutrients are used
up it subsides. So plankton bloom is essentially a rhythmic affair linked
with the season and temperature changes. Following the surge in plankton
number, the density of fishes which feed on these planktons also rises up.
Sept
Plankton
bloom
Nov
Jan
Mar
May
Months
Jul
Sept
Fig. VIII.6 Plankton bloom in spring.
Adaptations and
Evolution
h. Each environment has its own characteristic demands which lead to
evolution of adaptive features. Such as, a brook is characterised with
swift-flowing water while a lake may scarely have any current. So a
brook-living fish would very likely have suckers on its lower surface (i.e.
ventral surface) to stay put at a particular spot as long as it needs while,
a lake fish would need only good fins to swin about. Thus demands of
environment encourage adaptations.
Here we shall present a few special adaptations in sedentary water or
lake-dwelling (lacustrine) beings:
(i) Aerial respiratory organs: Some of the pond fishes like Anabas
sp. (in eastern India) migrate from one pond to another when the
monsoon rains comes in June. This overland journey is frought with
dangers— dehydration as well as asphyxiation. To avoid dehydration these
migrate only in the nights, after rains when the grass is wet. To deal with
asphyxiation these fishes have developed a pair of spongy structures
behind their gills. These structure facilitate respiration in air (Fig. VIII. 6).
These are called accessory respiratory organs. Also these fishes have
spines on the rims of their gill covers (i.e. operculum) which help them
to move about in wet grass.
(ii) Lungfishes (Dipnoi). In Australia, South America and Africa
where they have many shallow ponds/lakes which regularly dry up in
summer. A group fishes living is such situations, besides having their
normal gill, have developed a pair of lungs as well which, enables them
to respire in air and thus tide ever the summer months. Protopterus is one
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183
of such fishes. These live in Africa where during summer they dig holes
in the muddy bottom, exude copious mucilege to build cocooms around
their bodies. Protopterus stay inside these cocooms in a curled-up posture
and enter into a phase called aestivation (like of diapause of silk-worms
during winter). In this position the fishes breath air and wait for the return
of monsoon and water (Fig. III. 9).
(iii) Barbicules amongst detritivores. Bottom dwellers, such as
catfishes like Clarias batrachas or carps such as Labeo calbasu are
usually detritivores. These fishes are mostly bottom dwellers of ponds
and hence detritivorus (i.e. those who eat detritus i.e. decomposing
biomaterials). Also the bottom area is usually dark. So these denizens of
dark have developed specially sensitive thread-like 'feelers' on their snouts
to feel their way about in search of food. These feelers are called
barbicules or barbicels (Fig. VIII. 7).
Accessory respiratory argan
Anabas sp.
Fig. VIII.7 Accessory respiratory organ of a fish.
Barbicules
Clarias batrachus (cat fish)
Barbicels
Labeo calbasu (carp)
Fig. VIII. 8 Barbicules and Barbicels of a catfish and a carp.
These are some instances of how the demands of environments lead to
specific adaptations. Every ecosystem has its own demands which leads
to the matching morphological, physiological and behavioural adaptations
to enable its inhabitants to survive there. Thus begins speciation.
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Ecology for Millions
i. Lakes origin in several ways. Some begin by accumulation of water
from surrounding places (called water-shed of lake) into depressions
created by movement of soil layers (tectonic movements) over millions
of years. Some are formed within the volcanic craters—which are large
mouths of volcanoes cooled and solidified as large cup-like depressions.
Now-a-days men are creating lakes within river valleys by damming
rivers for irrigation and power generation. Some such river lakes are very
large. For instance, Lake Kariba on Zambesi river of Africa is 30 km ×
75 km and Lake Nasser on river Nile is 300 km. × 50 km.
Origin and Size of
Lakes
j. Here are the names, locations of 15 biggest natural lakes of the world
(Table VIII. 2a, b & c). Amongst the huge lakes a few perhaps deserves
special attention. (1) Lake Baikal. It is the oldest (25 million years) and
deepest (1260 m.) in the world. It has its own characteristic fauna found
nowwhere else. 70—80 % of its fishes are unique. Baikal’s fauna is as
special amongst lakes’ as is Australia’s fauna amongst the continents.
98% of the arthropods ( prawns, crabs and such creatures) and 80% of
the fishes of Baikal are endemic (not found anywhere else). (2) Aral Sea.
It is a huge one nonetheless, the erstwhile U.S.S.R. has drawn so much
water out of it for giant irrigation projects that the lake has shrunk to
almost 1/4th of its original size with all harmful consequences. The
present status of the Aral Sea is a good example of how Nature should
not be handled. (3) Canada and U.S.A. are extremely fortunate to have
five huge interconnected lakes—Superior, Michigan, Huron, Eerie and
Ontario. Between Eerie and Ontario there is that huge and spectacular
Table VIII.2(a)
FIFTEEN BIGGEST NATURAL LAKES OF THE WORLD
(Adapted from various sources)
Rank
Name
Area (Km2)
Country
Remarks
Salty
1.
2.
3.
4.
Caspian Sea
Lake Superior
Lake Victoria
Aral Sea
371,000
82,900
68,800
65,500
USSR
Canada
Africa
USSR
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Lake Huron
Lake Michigan
Lake Tanganyika
Lake Baikal
Great Bear Lake
Great Slave Lake
Lake Erie
Lake Winnipeg
Lake Malawi
Lake Ontario
Lake Ladoga
59,580
58,020
38,900
31,500
31,330
28,570
25,680
24,890
22,490
19,400
18,390
Canada
USA
Africa
USSR
Canada
Canada
Canada/USA
Canada
Africa
Canada/USA
USSR
Now drying up (owing to mega-irrigation
projects)
Deepest (1260 m.) and oldest (25 million years)
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Biomes
185
Table VIII.2(b)
THE 15 LARGEST NATURAL LAKES OF THE WORLD
Name
Country and Comments
371,000
Caspian
USSR Main source of sturgeon
fish and cavier-their eggs.
2
82,900
Superior
Canada
5
59,580
Huron
Canada
6
58,020
Michigan
USA
11
25,680
Erie
Canada
and USA
14
19,400
Ontario
Canada
and USA
3
3
68,800
Victoria
Africa
4
4
65,500
Aral
7
7
32,900
Tanganyika
Africa
8
31,300
Great Bear
Canada
9
31,300
Baikal
USSR Oldest (25 million years)
and deepest (1260 m) Lake
10
28,570
Greal Slaue
Canada
12
12
24,890
Winnipeg
Canada
13
13
22,490
Malawi
Africa
15
18,390
Ladoga
USSR
1
14
5
2
No.*
Area
1
11
All the 5 lakes are
interconneated fed with
ice melt from north
Canada and open to
Atlantic sea via
Niagra falls at the
end of Lake ontario
and then St. Lawrence
river.
6
8
9
10
15
*According to size (area in Km2)
USSR Now owing to too much with
drawal of water for irrigation
it has shrunk to 40,000
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Ecology for Millions
Table - VIII.2(c)
DEATH SPASM OF ARAL SEA. IN 1960 ITS AREA
WAS 67,000 SQ. KM. AND IN 1997 ONLY 39,000 SQ. KM.
KAZAKHSTAN
150 Km.
N
1960
Aral
Sea
1997
E
Sa
yr
D
ar
ya
R
UZBEKISTAN
Am
u
Da
r ya
R
TURKMENISTAN
Niagra Falls pouring down 800000 thousand gallons of water per
second. All the surplus water from these five lakes come via Niagra Falls
to Lake Ontario and from here through St. Lawrence river to Atlantic
Ocean. Seeing Niagra Falls is an unforgettable sight.
k. Amongst the artificial lakes the two largest ones we shall touch upon.
first is the Lake Nasser created by dammging Nile at Aswan. It has
created a huge artificial lake about 300 km × 50 km. This lake has
submerged the huge and famous stone images at Abu Simbel. Fortunately
Egypt with international aids, has been able to cut these idols into
managable sizes and remove them to safe places before these were
drowned. The other one is the Lake Kariba—another leviathan of
300 km × 75 km created by damming Zambezi river at Kariba.
Interestingly another spectacular falls—the Victoria Falls lies at the other
end of Lake Kariba—also on Zambezi river.
Consequences of
damming the rivers
l. Damming a river makes water available for power generation and
agriculture. These are economic gains but not without a price. A dam
creates extensive changes in the local ecosystem and also in the flora and
fauna of the river. Unfortunately such changes are not being given enough
attention. In india owing to poor maintenance, most of the river dams are
being silted up. Also owing to melting of snow, deforestation and the
annual monsoon floods are increasing in ferocity. Still they are erecting
another huge dam—Narmada dam, the ecological fallout of which may be
far from welcome. Public is generally ill informed and Indian ecologists’
voice is too feeble to be heard.
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m. Lake fauna can be divided into three main groups. (1) Plankton.
These are tiny beings—both plants (phytoplanktons) and animals
(zooplanktons) who stay on the upper surface, photosynthesise, and are
not very mobile. (2) Nekton. These are mostly fishes and other animals
such as turtles, prawns, etc. who can swin about on their own.
(3) Benthos. These are organisms which are attached with the bottom or
live on the bottom sediments. For instance, Chironomid larvae* or
bloodworms, Tubifex **—a red annelid—commonly used as fish food in
home aquaria and Unio—a common pond bivalve *** etc.
n. The quality of the water of lake naturally depends upon the
surrounding area or the watershed from which water comes into it and
also the depth of the lake. Young lakes are deep and hence have a much
larger hypolimnion than epilimnion. The nutrient content is also relatively
low. Such lakes are called oligotrophic lakes. As nutrient content is low
so is plankton density. Such cold oxygen rich clear water lakes are
preferred by such fish as trout eutrophic lakes are older, shallower and
are richer in nutrient content. These therefore have high plankton density.
Kashmir’s Dal Lake is an eutrophic lake. Trouts cannot live in such lakes.
They prefer oligotropic lakes.
o. A lake is nourished with water from its watershed #. The watershed
nourishes the surrounding ecosystem including humanity. Consequently any
change in the watershed will effect the lake as well. With time, through
sediments from watershed, all lakes gradually get filled up and ultimately the
aquatic flora and fauna of a lake are replaced by terrestrial flora and fauna.
This however takes thousands, if not hundreds of thousands, of years. A
lake may also dry up owing to depletion of its water (as in Aral sea). So a
careful and alert observer may be able to discern stages of succession in the
shore of a lake. Such successions from aquatic to terrestrial systems are
known as hydroseral successions.
p. Nowadays the following factors, created by human intervention, are
adversely affecting many lakes.
(i) When trees in the watershed of a lake, are cut down the rain
drops falling directly upon the exposed forest floor will loosen the soil
and hence the rain water will carry more of silt with it than before. This
silt will untimaetly settle in the bottom of the lake raising the bed every
year. If this concontinues unabated i.e. unless corrective measures are
taken in time, soon the lake will meet its doom. The Dal Lake in Srinagar,
Kashmir, India, is a good example. This beautiful shallow lake, one of the
*from Chironomus—an insect.
**A species of Annelid—a group allied to earthworms.
***Bivalve—the group which oysters belong to.
#A watershed broadly means the area of land, from which rain water according to
gradient or slope, accumulates into a lake or river or swamp and thus maintains it.
187
Lake Fauna
Productivity of
Lakes: Oligotrophic
and Eutrophic
Lakes
Death of a Lake
and Hydroseral
Succession
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Ecology for Millions
attractions of Kashmir is doomed to death within next 100 years or so,
unless vigorous preventive measures are taken now.
(ii) Besides natural beauty lakes and swamps are very valuable in
recharging ground water. If lakes and swamps get silted up rain water will
very quickly roll away elsewhere leaving the groundwater unrecharged.
This is one of the reasons why in many densely populated areas and
tubewell-irrigated agricultural areas, the level of ground water is going
down every year. In U.S.A. parts of Florida Swamps have been drained
off by estate developers for making houses and villas. Now they are
having second thoughts. Situation in Kolkata, India is equally saddening.
For instance they are sinking a deep tubewell capable of lifting 35,000
gallons of water per hour in CD park of Salt Lake (Laban Hrad Sambad,
21.04.2004). This will very likely lower the ground water level further.
Plight of Kolkata
Ponds and Swamps
q. Kolkata a metropolis in eastern India, although receives more than
hundred inches of rain every year, suffers from water shortage in
summer. When the British colonialists created this town by buying out a
few villages, they established many parks, left many ponds untouched and
dug a few new ones—partly for beauty and partly to face summer
draught. Since 1947 i.e. Independance, the Kolkata people started filling
up the ponds to construct houses. Parks were nibbled here and there for
Government uses. The Government owned ponds are neglected, neither
their water is cleaned regularly, nor the sediments dredged out to maintain
their depths. On the contrary, the Kolkata people usually look upon a
pond as a convenient dumping ground for rubbish. Slowly the ponds are
dying. Roads and footpaths are being paved up. So when rain comes
Kolkata gets water logged. The sewarage canals are choked and parks
are few and the footpaths are all paved up. So the rain water has no
chance to percolate into the soil and recharge the ground water. Hence as
soon as the rainy season is over, Kolkata faces draught. Wells dry up as
the water level gose down. Trees on foothpath die—as they have paved
the footpath right up to the base of the tree—so the base of the tree has
not received any water during monsoon. Most of the city canals do not
have running water any more—although they were planned so; so these
become cess-pools and happy breeding grounds of mosquitoes and
sources of other problems of hygiene. A once-beautiful lake in Lake
Town is slowly being killed to make way for houses (Photo V.1a).
Now they are even filling up the swamps around Kolkata for housing
projects. None who counts seen to understand the value of swamps. The
entire Salt Lake City of Kolkata is made that way. Now they are planning
to reclaim more such swamps around Kolkata. It seems that more
miseries lie ahead. The only consolation seems to be that people are
unaware of the ominous future—so for the time being they seem to be
happy. In short, Kolkata is a good example of mismanaging nature.
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1.3 Streams and Rivers
Streams and Rivers are stages of the same system—drainage system for
water of watersheds. The water may come from melting of ice from
snow capped mountains (as in Himalayas) and or from rains. As water
always flows in streams and rivers the communities living in such waters
are called Lotic or running water communities.
Streams and Rivers
a. Basically there are three important differences between a pond / lake
community and a stream / river community. First is the—Water
Current: Here in lotic systems, water always flows. So all organisms
have to adopt themselves to a life in flowing water or, they would be
carried away to altogether different places. So among lotic organisms
some have hooks, some suckers, some strong claws, some digging
apparatus and some are very strong swimmers etc. Such adaptations are
required to keep them where they need to stay. The second differences is
oxygen content : As the water is always flowing and depth is not much,
Oxygen Content in lotic water is uniformly high. Consequently unlike
lentic communities (i.e. communities in ponds or lakes) which can tolerate
oxygen fluctuation to a considerable degree, the lotic communities (i.e.
communities in streams or rivers) are very susceptible to oxygen
depletion. This suseptibility is successfully used by forest rangers to test
the quality of waters of streams and rivers (more about this in next
chapter when we shall talk about BOD). Thirdly, as all streams and rivers
are shallow water and running water systems there is no Hypolimnion in
lotic waters. So the entire water contains photosynthetic and
heterotrophic organisms.
b. Streams and rivers differ from each other mainly in gradient, speed of
water current and width of the valley. At her origin, a river is more like a
stream; her sides are steep, water flow high and the valley is narrow and
steep. As the river flows forward she widens, her water speed reduced and
she joins up with other such sister rivers, who bring waters from different
part of the same valley or adjacent valleys. Gradually this river moves
forward, and strengthened by unions with sister rivers, so the river
becomes wider, her gradient gentler and the water speed is further reduced.
In the final stage when the river reaches its lowest level and its speed
becomes slow or sluggish, the silt deposition is high as a result deltas are
formed.
In short there are three distinct zones in the watershed of a river.
First the steep-gradient, high-speed and cold water zone in the
mountainous areas, second the medium gradient and medium-speed and
relatively warm zone in the plains and in the third or final stage a river has
a very low gradient, low-speed and fairly warm water zone. Here is the
confluence of the river with sea or a lake. Also here deltas may form.
c. Streams and rapids in cool high mountain, where the water is clear
and the current is high, there are boulders which create small pools.
Zones in a River
Watershed
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Ecology for Millions
Importance of
streams and rapids
in fish breeding
These are favourite breeding grounds of fishes such as salmon. These
fishes, which spend most of their adolescent and adult days in seas when
breeding season comes, return swimming all the way up from the sea into
the river and from the river mouth to nearly the origin of the river—rapids
in high mountains to lay their eggs. These eggs are laid in nearly the
same spots where they were born a few years ago. The Atlantic sock-eye
salmons which spend most of their lives in various locations of Atlantic
return to lay eggs in the source areas of rivers in western Alasca. Here,
in small rock pools of cold clean water these fishes spawn (Fig. VIII. 9).
It is a wonder how they perform this perilous return journey of thousands
of miles following only the dictates of their genes. When men dam up the
rivers and thus prevent such fishes from swimming up to their breeding
grounds, the fish population plummets. So now they have added fishladders to enable such fishes to move up the dam and breed as before in
their normal spawning grounds (Fig. VIII. 10).
Fig. VIII.9 Spawning bed of Atlantic salmon-Salmo sp. (schematic).
Fish Ladder with Salmons
DAM
Fig. VIII.10 Fish ladder for river fishes to negotiate dams and continue their swim upwards.
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Biomes
d. Recently it has been found that whereever in a rivershed there has
been logging, the enhanced soil erosion has made the waters somewhat
turbid and silt loaded. Fishes do not lay eggs in such rock pools there any
more. Owing to deforestation so much damage has taken place in
spawing areas that salmon population has dwindled and so salmon fishing
suffered. This is a poignant example how even an apparently small change
in one part of the ecosystem can swell up into a major upheaval. Many
such things are happening in Himalayan forests and the snow lines above
them where lies the sources of three major rivers of Indian
subcontinent—Indus, Ganga and Brahmaputra. Unfortunately as yet not
much is known about the consequences of such actions. Things must be
happening only people are blissfully unaware.
e. In many aquatic systems a new but deleterious factor has been
introduced by men. This is eutrophication. Broadly eutrophication means
enrichment of the environment with nutrients in such a way that
productivity (i.e. production of biomaterials) is increased. This begins
with the increase in phytoplanktons. A consequential biological
phenomenon of eutrophication is increase in biological oxygen demand. By
Biological Oxygen Demand (BOD) we mean the amount of oxygen
needed to completely oxidise all the organic and chemical wastes in the
water until the water is clean again.
f. The sewerage water which is full of organic and chemical wastes
(which are, in-a-way, nutrients) is cleaned in the following way. Before
being released into the rivers or recycled for gardening and agriculture, all
the large particulate dirt is sieved out. This is first treatment or primary
treatment. Then water is transferred to secondary treatment plant where
microorganisms carry out the breakdown and assimilation process till most
of the organic matters and chemical nutrients are used up. This is
facilitated by supplying oxygen to the waste water by aeration. Primary
treatment removes about 35% and secondary treatment about 55% of
BOD so these two treatment together have about 90% efficiency in
reducing BOD. To make the water usuable in homes however requires
further treatment or tertiary treatment which involves various processes
such as electrodialysis, and chlorination etc.
g. In poor countries like India, Pakistan, Bangladesh etc. water supplied by
most municipalities may not always be very good in quality. Dysentry,
cholera, jaundice, ptyphoid, all are caused by water borne carriers. It
seems to us the best thing to do is to either treat the municipality—water,
in small home water—treatments plants where special filters and U.V.
lights are used or better still to boil the water or, use solar-distillation
plants to distil water before using it for drinking purpose. Then most of
the above ailments will vanish.
191
Logging in watersheds and its
effects on fish
spawning
Eutrophication,
BOD and treatment
of waste water
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Ecology for Millions
1.4 Estuaries or Deltas
The region of a river where it opens into a sea covering an extensive
shallow tidal area is called estuary. The rivers here are shallow, wide and
many have split out from the main river. The water is brackish i.e. the
salinity is in between sea water and fresh water.
Estuaries
High productivity of
estuaries
Estuaries in Ganga
delta and its pitiable
fate
a. The estuarine water is very rich in nutrients. This is because the lighter
freshwater from the river flows outward forming the top layers while the
heavier salt water from the sea flows inwards forming the bottom layers.
(Fig. VIII. 11). This counter current forms a sort of nutrient trap
enriching the estuarine water and raising its productivity. Besides the
enrichment of estuarine water through nutrient trap, most estuarine water
is also enriched from accumulation of dead and decaying products (i.e.
detritus) from mangrove vegetation (described earlier III6.3) of estuaries.
Consequent upon all these the estuarine biomes are one of the highly
productive biomes of our biosphere. Their average net primary
productivity is of order of 200-3500 gm/m 2/year. In the end of this
chapter a comprehencsive table showing the productivities of all biomes
discussed here are given (Table VIII. 3).
b. In the South Bengal—both of India and Bangladesh there is an extensive
estuarine biome formed by Gangetic delta. This is Sunderban. In not too
distant past—about 100 years, it was a large and lovely biome—home of
one of the most regal animals of the world—the Royal Bengal Tigers
(Panthera tigris) and innumerable other attractive animals and plants. The
well known amongst then are deers, honey bees and prawns, shrimps,
crabs, and many fishes and trees like ‘Sinduri’ ‘Goran’ etc. etc. It is still
a much smaller but a lovely biome—and a visit to it would leave pleasant
memories with any one. But to-day its future is dark. From the beginning
of this century however Sundarban is slowly being chipped off; first by
middle class ‘Bengali’ ‘babus for making “bheries”—a system of
impoundment of tidal water for fishery, and by poor Bengalis as easy
source of wood as fuel. After independence i.e. since 1947 things have
aggravated so much that Sunderban is simply being raped. The greed of
River water
River
Sea water
Nutrient trap
Fig. VIII.11 Two opposite currents in estuarine water forming a nutrient trap.
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193
Table VIII.3.
BIOMES AND THEIR PRIMARY PRODUCTION AND SUCH RELEVANT INFORMATION
(Adapted from Colinvaux, – Table – 24.3. p. 508)
Mean Net Primary
Productivity (g.c/m2/yr)
Area (106 Km2)
[% in bracket]
Total Net Primary Production
(109 metric ton.yr.)
[% in bracket]
1. Tropical Rain Forest
2. Temperate Evergreen Forest
3. Temperate Deciduous Forest
4. Boreal Forest
5. Woodland, Shrubland
6. Savanna
7. Tundra
8. Desert
9. Others (incl. agri.)
900
585
540
360
270
315
65
32
298
17.0 [11.765]
5.0 [3.460]
7.0 [4.844]
12.0 [8.304]
8.0 [5.536]
15.0 [10.380]
8.0 [5.536]
18.0 [12.457]
54.5 [37.370]
15.3 [33.579]
2.9 [6.368]
3.8 [8.344]
4.3 [9.442]
2.2 [4.831]
4.7 [10.320]
0.5 [1.098]
0.6 [1.317]
11.24 [24.681]
TOTAL LAND (28.333%)
374
144.5 (99.580)
45.54
1. Swamps
2. Ponds, Lakes and Rivers
3. Open Ocean
4. Upwelling Zones
5. Continental Shelf
6. Coral Reef
7. Estuaries
8. Others
112.5
225
57
22.5
162
900
810
–
2.0 [0.547]
2.5 [0.684]
332.0 [90.834]
0.4 [o.109]
26.6 [7.278]
0.6 [0.164]
1.4 [0.383]
–
2.2 [7.942]
0.6 [2.166]
18.9 [68.231]
0.1 [0.361]
4.3 [15.523]
0.5 [1.805]
1.1 [3.971]
–
TOTAL WATER (71.666%)
500.6
365.5 (99.998)
27.7
437
510.0
73.24
Biomes
TOTAL OF EARTH
money of industrialists and craze for vote bank by politicians together are
choking Sunderbans almost to death. Now they are even talking of
erecting an Atomic Power Station there. That will be the last nail in the
coffin of India’s pride—the Royal Bengal Tigers. The ecological backlash
of the destruction of Sunderban we shudder to think of. More has been
discussed on this issue in IX.
c. Sundarban’s survival needs serious serious ecological works and
vigorous administrative actions which are unfortunately scarce. As far as
we are aware of two scientists are working. Dr. Kumudranjan Naskar
and his team are working on Sunderbans mangrove flora (2004) and
Prof. Amalesh Roy Choudhury (1987) has established, through his own
initiative, a small Marine Biological Station at Sagar Island in the mouth of
Ganges. These are very heartening efforts but not enough.
1.5 Coral Reefs
a. Coral Reefs, continental shelves, open oceans and upwelling zones are
four biomes which are parts of sea. These share certain common
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Ecology for Millions
Common features of
all seas
features. (1) Salinity: Sea water has a very high salt content, about 3%.
This is more than what sea animals have in their bodies. Consequently
water tends to get out from sea animals bodies into sea. Therefore to sea
animals sea is a dry place. This is reverse of what happens to fresh
water animals. (2) Depth: Depths in sea vary from 5 metres in coastal
waters to 8000 metres or more in really deep portions of sea (trenches).
Naturally marine animals are subject to extreme variations of pressure.
Those who inhabit shallow water can’t stay in deep waters and vice
versa. Sharks, whales and a few other marine animals however, can bear
enormous variations in water pressure. So these can easily roan about in
deep waters and again come up and swim about in shallow waters. (3)
Light: Sunlight cannot penetrate effectively beyond 300 metres in water.
Therefore, out of a total possible depths of 8000 metres or so only the
top thin layer of 300 metres or so is productive i.e. the autotrophic zone.
(4) Current: Owing to rotation of earth on its own axis, sea water is
constantly moving. Hence there is a constant, fixed and worldwide ocean
current (Fig. VIII. 12).
Coral Reef
b. Coral reefs are shallow and relatively warm areas of sea where corals
grow in abundance lending a beautiful under-water colourscape like look
to the whole area. (Corals are small marine polyp—like animals who have
a calcaroous skeleton. After death of these polypes’ skeleton get deposited
one above the other—gradually forming what we know as coral reefs).
These areas are very rich in nutrients as coral reefs are within autotrophic
zone of sea and act as resting, hiding, feeding and breeding places of
many marine animals—particularly fishes. Coral reefs abound with
beautifully coloured fishes, such as sea horse, butterfly fishes, crabs, seaanemones, sea stars, corals, cray fishes, mussels, octopuses, small fishes
Fig. VIII.12 Continents, oceans and major currents of the oceans.
(In northern hemisphere currents are clockwise and in the
southern hemisphere anticlockwise).
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195
and many more. In fact diving into a coral reef in a divers’ suit and
seeing the throbbing life of coral reefs is an unforgettable experience.
c. The most famous coral reef of the world is the Great Barrier Reef of
Australia skirting almost half of eastern coast of Australia like a huge tiara
stretching 1500 miles from Brisbane in South to the Cape York Peninsula
in North. Others are found nearly in almost every Pacific Islands and
other shallow warm water areas. In India there are a few excellent coral
reefs—Andaman and Nicobar Islands, Palk Straits and Gulf of Kutch.
Gulf of Kutch is particularly interesting as this is a small gulf spreading
from east to west and has tidal height of 13 feet or so. Hence it is
extremely rich in diversity of marine fauna. The author and his students
have found living conch shells, small octopuses and small dog fishes (a
species of shark) in puddles of water left in low tides amongst the coral
reefs.* The entire Gulf of Kutch should be made a “reserve marine
forest” by Govt. of India as soon as possible. Some steps have already
been taken. Also this Gulf can be safely used to generate electricity from
tide when water rises about 12-14'—a clean source of power and a
permanent one.
d. Coral reefs are one of the most beautiful spots of Nature. Anybody
who is a good swimmer can enjoy them. One however must never
venture into a coral—reef without supervision of a local expert diver or
else, pleasure may soon end up in pain. The most frequent dangers in
these places are sharks, sting-rays, poisonous jelly-fish, electric cels and
coral snakes (Fig. VIII. 13a, b & c).
A Tun shell
Great Barrier Reef
and other famous
coral reefs
Gulf of Kutch
Pleasure and pains
in visiting them
A sea star
Fig. VIII.13a Some animals of coral seas. A snail and a starfish.
*The author has published a detailed study on the Pelecyphods (musssels) of
Gulf of Kutch (J.B.N.H., 62, 1 and 2).
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Ecology for Millions
A Foraminifera (one celled animal)
(Protozoa)
Live
Shell
A scoliodon (dogfish)
Fig. VIII.13b A Protoroan and a Dogfish.
Sea horse
(Hippocampus sp.)
Poisonous Jelly Fish
(Physalis sp. )
Fig. VIII.13c A sea horse and a poisonous Jelly fish.
e. Unfortunately however, the advancement of fishing techniques
particularly dredging by trawlers which scoop up the whole bottom biota
—corals, star-fishes, algae and all and killing fishes by poisoning the
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197
water and using explosives are posing grave dangers to marine
ecosystems. Some species are facing extinction. One such is seahorse
(Hippocamous sp.) and small beautiful horse-like fish which has a mouth
like a horse and prepensile tail with which at attaches itself to algae (Fig.
VIII. 13a, b & c). Most Governments are yet slow to grasp the gravity
of the situations and act.
1.6 Continental Shelf
a. Continental shelf, open ocean and upwelling zones, although all these
three form parts of a continuous environment namely oceans, still they
are remarkably different from one another in their areas, depths and
productivities. A summary table given here will illustrate this point
(Table VIII. 3).
Continental Shelf
and different zones
of the sea beyond
continental shelf
b. The above table we shall come to later. First let us summarise the
outstanding features of continental shelf. The continental shelf is that
segment of ocean which skirts all the continents as a shallow water zone
extending as a step 10-150 miles wide and not deeper than 200 metre.
This area is within the penetrable zone of sunlight, hence euphotic. But
this is beyond the Littoral zone which is washed daily by tides.
After the continental shelf there is a sharp drop of ocean floor i.e. rise
in depth from 200 to about 3000-4000 metres. This zone forms the bulk
of the ocean floor. The lower part of this zone is called the Bathyal
Zone and the upper part—the euphotic—the open ocean. In some zones
the ocean floor suddenly drops further till 8000 to 11000 metres. These
are called Hadal zones with individual names such as Maryana Trench in
the Pacific ocean. Maryan trench is the deepest trench of the world
(11,600 metre). In fact it is the reverse of the Mount Averest (highest
mountain in the world). Mount Averests’ top will be more than 1/2 mile
under the sea if it is dipped in Mariana trench. There is an excelent article
on ocean floor in a recent issue of National Geographic Magazine.
c. Now about the continental shelf. First : Light. Some of the sunlight is
reflected away from ocean surface. However red, orange and ultraviolet
lights are mostly absorbed in the first 25 metres of the surface. Green,
yellow and blue penetrates further till about 125 metres or so. Because
only green, yellow and blue colours penetrate deeper waters, sea-weed in
the deeper waters of continental shelf have a red colour pigments instead
of Green chlorophyll, for photosynthesis. Hence occasssionally we find
red-coloured weeds in the sea shores. Due to its shallow depth the
continental shelf receives sunlight and hence this zone is euphotic (see
Fig. VIII. 14) and photosynthetic Second : Biota. As continental shelf is
photosynthetic it has good density of diatoms (one celled plants),
foramifera (one-celled animals), and copopods (small prawn like animals),
jelly fishes, starfishes, fishes, sea-shells and worms etc. who feed upon
the smaller ones (Fig. VIII. 13). Diatoms contain silicon in their bodies—
Flora and Fauna of
continental shelf
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Open sea
continental
shelf
Nerilic
Ecology for Millions
Littoral
198
5 m.
200 m.
200
to
4000 m.
E
U
P
H
O
T
I
C
Pelagic
Sunlight
penetrates
A
Bathyal
P
H
O
No
sunlight
T
Trench
4000
to
10,000
m.
Hadal
I
C
Fig. VIII.14 Zonations of oceans: based upon—(a) tidal effect,
(b) depth of water and (c) penetration of sunlight.
hence these are siliconaceous and as Farminiferams contain calcium in
their bodies these are calcareous. When these die and their bodies settle
and rot upon the ocean floor these form a soft whitish mud called “ooze”.
Tides and wave action however at times, stir up the waters of continental
shelf. So the water of Continental shelf is fairly rich in nutrients, and
hence constitutes one of highly productive areas of sea (Table VIII. 3).
d. Fishing vessels of most of the countries operate mainly in continental
shelf. One very interesting fish of continental shelf is tuna (Orcynus
thynnus). This fish is so large (2-3 metres), so delicious and so expensive
(5-10 thousand dolars a piece) that American fisherman use helicopters to
locate them, harpoon to kill them and big trawlers to lift them from sea
and then immediately freeze and fly these to Tokyo fish market—the
greatest fish market of the world. Japanese love to eat ‘suci’ a delicacy
made from tuna. So the ultimate destination of most tunas of the world
are the Japanese kitchens.
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1.7 Open Sea
a. Open sea is the vast expanse of sea beyond the continental shelf,
whose average depth is 2000-4000 metres. Its upper part receives
sunlight hence euphotic but lower part does not—hence aphotic (Fig. VIII.
14). The euphotic area is known as pelagie and aphotic area as bathyal.
Open sea covers around 70% of earths’ surface and interconnected
throughout the world and holds 97% of earth’s water. Columbus rightly
thought that as the seas are interconnected so if he sails west he will
arrive at the east. It is dreamers like him with courage to act change the
world. The folowing table gives some information about the oceans and
major seas of the world. This includes continental shelves as well, as
these are part of seas. (Table VIII. 4).
Open Sea
b. The tidal waves and oceanic currents mixes the upper waters about 300
metres or so, rest of the deeper waters remains unaffected and cold—about
3°C. The productive zone of the open sea is only the thin top layer of 200
metres or so which receives sunlight and so is photosynthetic. The detritus
settled in the bottom of the open sea, which is 3-4000 metre below and
hardly has any current. There this remains locked up for hundreds of years.
Only a fraction fo it comes up to the surface through upwelling (see later).
So the concentration of nutrients in open sea is rather low and consequently
is the productivity (Table VIII. 1). In fact open sea is comparable to the
deserts of terrestrial systems.
Poor productivity of
open sea and its
cause
c. Notwithstanding, open sea harbours some very spectacular large
swimmers (nectoms) such as blue sharks, blue whales, baleen whales and
rorquals, turtles, great white sharks, large octopuses, cuttlefishes,
porpoises and flying fishes etc. (Fig. VIII. 13). Whales are the laviathans
of the ocean. They are a large group of aquatic mammals classified into
three families and consisting of 76 species some toothed some toothless.
Table VIII.4.
MAJOR OCEANS AND SEAS OF THE WORLD AND THE WATER THEY HOLD
(From – Colinvaux, p. 373, Table – 15-1.)
Name
Pacific Ocean
Atlantic Ocean
Indian Ocean
Arctic Ocean
South China Sea
Caribbean Sea
Mediterranean Sea
Bering Sea
Gulf of Mexico
TOTAL
Area (103 Km2)
Volume of water (103 Km3)
165,250
82,440
73,440
14,090
3,685
2,755
2,515
2,270
1,555
348,000
707,600
324,600
291,000
17,000
3,905
9,585
4,250
3,300
2,230
1363,470
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There are 66 species of toothed whales (Odontoceti) some of these are
small 4 to 8 feet long such as river dolfins and are somewhat bigger-such
as the marine dolfins and porpoises who are very intelligent and playful.
Dolphins are easily trainable and star attractions of marine aquaria all over
the world. The largest of this group are the sperm whales. There are 10
species of toothless whales (Mysticeti) which are also called baleen
whales. Some the pacific grey whales and all the remaining species of this
group has baleen which consists of fine bony plates arranged in the form
of two combs hanging from the upper jaw (Fig. VIII. 15). Baleen whales
feed by opening their mouth wide and then rush through water so that all
small fishes, prawns, jellyfishes etc. get into their mouth along with
waters and then get trapped into their mouth only to be eaten by the
whale. Because they have to feed by sieving a lot of water at ago all
whales are good swimmers with sleek bodies and characterised by small
dorsal fins. The famous blue whale (Balenoptera sp.)—the biggest animal
of earth (100 ft. long) is a baleen whale and a denizen of open seas (Fig.
VIII. 15).
The famous novel “Moby Dick” by Herman Melville is a captivating
story of a blue whale and his heroic struggle for survival.
1.8 Upwelling Zones
a. There are certain areas in sea where deep ocean currents of cold
water striking upon a submerged range of mountains wells up towards
the warm surface carrying along with it all the rich nutrients accumulated
into the sea bed. Such areas of sea surface where water of the surface
mixes with the rich cold water welling up from the bottom are called
upwelling zones. These places are very rich in plankton and fishes. Sea
birds always swarm over such areas. Such up-wellinig zones are the
BALEEN
Fig. VIII.15 Baleen of Baleen whales.
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happy hunting grounds of marine birds and now trawlers. One such area
is in the west of south America and another in the west of Africa. More
has been given about upwelling in
There is story book “A Bridge of Magpies” by Geoffrey Jenkins,
1975, written about the guano deposits (sea-birds droppings) owing to this
west African upwelling zone.
b. The summary table VIII. 3, shows the primary productivities and
productions of all the main biomes and their areas of earth. This should
be a very useful information to all concerned.
2. TERRESTRIAL BIOMES
a. Just as we have water as the constant abiotic component of the
environment in all aquatic biomes similarly, for all terrestrial biomes soil or
land is the constant abiotic component. Also, unlike sea which is
continuous land is more fragmented into continents and islands with vast
expanses of sea standing as nearly impassable barriers for animals and
plants. As a result of this isolation, land biota* of different continents have
evolved into somewhat distinctive types in each continent or area. These
areas characterised with distinctive flora and fauna are called
Biogeographic Regions with names as follows (Map VIII. 1).
Special features of
Terrestrial Biomes
I
Palaearctic
V
Nearctic
III Oriental
VII
Galapagos
African
II
Neatrofical
VI
IV
Australian
Map. VIII.1 Biogeographic regions of the world, indicating Galapogos Islands as a distinct region.
*Biota = flora (i.e plants) and fauna (i.e. animals).
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Biogeographic
Regions and some
distinctive animals
Ecology for Millions
(1)
(2)
(3)
(4)
Nearctic (North America)
Neotropical (South America including Mexico)
Palearctic (Europe and Asia)
Oriental (India, Pakistan, Afganistan, Myanmar, Thailand,
Combodia, Malay, Sumatra, Borneo and Philipphines)
(5) African (Africa and Madagascar)
(6) Australian (Australia, New Zealand Tasmania and New Guinea).
b. These Regions are separated from each other for millions of years. So
each region have some remarkable animals and plants not found in any
other regions. Here are a few such.
Nearctic
— Caribou, Bison and Mountain goat
Neotropical — Monkeys with prehensile** tail (such as howlers,
spider monkeys), Ostriches, Armadillo, Rhea and
Condor.
Palaearctic — Reindeers, Giant pandas and Wild horse.
Oriental
— Tigers, Baboons and Flying Lemurs.
African
— Zebras, Giraffes and Gorillas and 2 horn Rhinos.
Australian — Kangaroos, Dingo dogs (now extinct) and Platypus
(egg laying mammal).
Galapogos — Giant Land Tortoises, Darwin’s finches, sphenodon
Island
etc.
A word about
Galapogos Islands
and Darwin’s
Voyage
c. It seems injustice would be done to our readers if we move on without
dwelling for a while on Galapogos Islands—a biological wonder land.
Galapegos is a set of 12 small valcanic islands in Pacific ocean and is
situated at the crossing of equator with 90° longitude about 1000 miles
west of Ecuador. These islands were discovered in 1535 by Fray Thomas
de Berlanga, Bishop of Panama. Charles Darwin, the author of the single
most famous book on biology “Origin of species”, 1859. set his foot on
Galapogos Islands 300 years later on 16th September 1835, travelling as
an unpaid gentleman biologist in H.M.S. Beagle with its Captain Robert
FitzRoy.
d. During these 300 years Galapogos was a usual stopover for ships
particularly whalers who picked up the huge land tortoises from there to
replenish their meat store. None noticed any specialty there for these 300
years. It is Charles Darwin with his keen power of observation backed
up with knowledge of Biology and Geology and almost uncanny ability to
take in both analytical as well as synthetic view on the same set of
observations, immediately noticed that Galapogos biota is very different
from the biota of rest of the continents. Darwin also possessed a mind
that was unusually free from orthodoxy prevalent at that age. The seed of
doubt that was laid them in the fertile mind of Charles Darwin (he was
only 23 then) soon crystallised and resulted in that celebrated theory on
**Prehensile = adapted for holding something by entwining it.
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“The Origin of Species by Means of Natural Selection” made public in
1859. After publication of this book Biology has never been same as
before. (Later it became known that another British naturalist Alfred
Russel Wallace was working at the same time in the jungles of south east
Asia and arrived as the same conclusions as Darwin. So now this Theory
of Natural Selection is known as Darwin-Wallace Theory of Organic
Evolution Through Natural Selection). So albeit its tinyness this cluster
of islands of Galapogos is fit for honour of a separate Biogeographic
region.
e. Anybody who wants know more about Darwin’s voyage in the Beagle
and his fateful visit to Galapogos may read. “Darwin and the Bengle” by
Alan Moorehead (Penguin Books 1971). Indeed the book is a biological
thriller. Darwin’s host i.e. skipper of HMS Beagle, Captain Robert
FitzRoy who was a devout christian, and earnestly believed in Special
Creation declared in Bible, was so shocked at Darwin’s heretical theory
that, many ascribe Darwin’s theory as the reason for which Captain
FitzRoy committed suicide even after promotion as Rear Admiral. FitzRoy
felt had he not taken Darwin as his guest in Beagle such a heretical
thought would have never seen the light of the day. Darwin was neither
knighted nor given an F.R.S. Thus one pays the price for challenging
tradition and faith.
f. Now let us come back to the point—the terrestial biomes. The
terrestrial biomes have three features which vary.
(1) Climate. Depending on its distance from the equator i.e. latitude.
Broadly there are five different climates for terristrial biomes
(Map VIII. 2).
North pole
Main features of
Terrestrial Biomes
North pole
80°N
15
60°N
15
15
40°N
15
20°N
15
0°
20°
40°
60°
South pole
South pole
80°
Map. VIII.2 Terrestrial biomes (a) Tropical, (b) Subtropical, (c) Temperate evergreen,
(d) Temperate deciduous, (e) Bareal, (f) Arctic (limits are approximate only)
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Ecology for Millions
(2) Plants. Depending upon the position of its renewal organs i.e.
organs with which a plant renews itself (also called prenating organs),
plants of the world are grouped into six different classes by a Danish
botanist Christen Raunkiaer (1934), Fig. VIII. 18. These are
Epiphytes—stay and flower on other plants–no roots to soil.
(i) Phanerophytes—Plants whose renewal buds are well above
ground as trees, shrubs etc.
(ii) Chaemophytes—plants whose buds are near the ground.
(iii) Hemicryptophytes—plants whose buds are just below the surface
of the ground.
(iv) Geophytes—plants where buds are well below the surface as
rhizomes or buds.
(v) Therophytes—plants which are annuals and survive only as
seeds.
(3) The third feature is the Soil. Besides moisture and temperature soil
is the third most important feature of a terristrial biome which influences
the nature of its biota. Hence soil needs some attention. All soils are
products of long-term (millons of years) weathering of parent-rocks and
accumulation and layers of silt (due to the actions of wind, water and ice)
and by-products of plants and animals living above and within soil. These
are arranged in the form of layers one above the other with the parent
rock forming the bottom layer and organic litter the top layers. These
layers are collectively called soil profile the quality of which varies widely
from place to place. The basic features of soil profile are shown in the
following (Figure VIII. 16).
HORIZON - A
Consists of litter humus
and top soil
HORIZON - B
Consists of mineral soil
and some humus
HORIZON - C
HORIZON - R
Fig. VIII.16 Soil profile (schematic).
Weathered parent material
Parent material
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g. Climate (temperature and rainfall) and soil (depth and richness of the
profiles) are the two features which guide the destiny of a terrestrial
biome—i.e. if it is going to be a rainforest or a desert etc. Now let us
examine the terrestrial biomes one by one.
2.1 Tropical Rain Forests
a. Tropical Rain Forests are the jewels of terrestrial biomes. These as the
name implies are situated in tropical regions and enjoy frequent rainfall
and warm weather throught the year. Their productivity is one one of the
highest of all the biomes (Table VIII. 3). They have an extremely
variegated flora and fauna and average temperature is of the order of
twenty five—thrity degree centigrade and annual rainfall of 100" or so.
The primary productivity can easily exceed 2 kg/sq/m/yr and sometimes
can even reach a fantastic value of 3.5 kg/ sq/m/yr! For their main
locations please see the Fig. VIII. 17.
High Productivity
and rich flora and
fauna
b. Tropical rain forests are dense humid and dark forests. These forests
is so dense that in a vargin rain forest not much of sunlight reaches the
ground—so the ground remains pretty clear of grasses and shrubs. Such
forest has three distinct layers or canopies. The top canopy consists of
very tall trees (34-40 metres), a middle canopy of shorter trees and a
bottom layer of a few scattered fern type plants. Besides these, there are
a lot of thick climbers in such forests. (Refer to downwords discription
in Benglis journey).
c. Tropical rain forests are also the habitat of a host of very interesting
animals. For example—army ants (Echiton burchelli), gibbon (Hylobatis
lar), large and spectacular butterflies, 3 toed sloth (Bradypus variagatus),
Fauna of Tropical
Rain Forests
Russia
North
America
Europe
China
Tr of cancer
India
Africa
Equator
South
Tr of sapre
America
Australia
Rain Forest Areas
Fig. VIII.17 Present rain forests of the world.
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Harpy eagle (world’s largest eagle), poison arrow frog (Dendrobates
auratus), anacondas or reticulated pythons (Eunectes sp.) who mostly
live in water and can be very huge (9 metres or so) etc.
d. Tropical rainforests are also a rich store house of medicinal plants.
One example is Cincona tree. The famous anti malaria drug quinine is a
product of Cincona tree from South America. The Cincona plant is
known as one of the few plants that have profoundly affected the course
of human history (the others, are Cotton, Potato, Sugar and Tea). The
natives of South America used to drink the bitter water of ponds into
which leaves from the surrounding Cincona trees fell and rotted, to cure
them of malaria. Jesuit preists of Spain noticed this and extracted quinine.
They kept this knowledge as a closely guarded secret and used quinine
as an incentive to convert the native Indians to Christianity and also sell
the quinine in Europe at the price of gold. Adventerous and clever
Britishers when they learnt of this secret, brought some saplings of
Cincona plants to manufacture quinine. Thus quinine has not only saved
innumerable lives all the world but also contributed to explosive growth
of human population. There are many other plants of medicinal value in
both old and new world about which we have only just began to
understand.
Now researchers from both sides of Atlantic are roaming all over
Afrika, South America and India looking for such plants and their
properties.
e. Trees valuable as timber such as teak (Tektona grandis) and sal (Shorea
robusta) are found in east of India, Myanmar, Malayasia, Philipines and
Borneo. There are many other valuable timbers in the rainforests of
Africa and Brazil. Unfortunately good rainfall throughout the year and
presence of excellent timber have also caused their doom. Large tracts of
rainforests have been cut down in South American and elsewhere to
make way for agriculture/animal husbandry and to obtain timber. To-day
we do not have even half of rainforests we had 100 years ago. The
situation is really alarming. I pray rich people to do something to halt this
stide.
Plunder of
Rainforests
f. Now-a-days many organisations particularly United Nations is trying to
save the remaining reinforests as sites of “World Ecological Heritage.” But
progress is poor, and in the meantime relentless pressure on reinforests
by various multinationals continue unabated. Poverty and population
pressure are the two major threats to rain forests. Governments of these
countries are selling their invaluable rainforests to various multinationals
just for money—particularly dollar. In Kolkata one frequently comes
across trailer-trucks carrying huge logs of sal (Sherea robusta), 3' of more
in diameter and 30' or more in length all from Malayasia. It is a painful to
see such pathetic ends of these magnificient kings of forests. Most of the
Pacific island between Northern Australia and Singapore are selling their
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Biomes
timbers. As a result of this denudation of rainforests those countries are
suffering from more floods and other calmities. Loss of rainforests will
not only harm these countries but will also deal a terrible blow for global
ecobalance. India's rainforests are mostly gone only a little is left in the
eastern and some in the southern tip of India. India is as tardy in taking
effecting steps to stop this plunder as other underdeveloped countries are.
2.2 Temperate Evergreen Forests Or Temparate Rain Forests
a. Beyond tropic of cancer and capricorn as one moves towards the poles
the weather becomes cooler but not too dry. Rainfall is good, around 4080". It is well distributed during the year—so there is no real dry period.
The prominent trees in these latitudes are usually broad leaved evergreens.
Such as oaks, beeches and the magnificant world famous Californian red
woods (Sequoia gigantica)—the tallest trees of the world, 90-100 metres
in length with a basal diameter of 5 metres or so!
b. Such temperate rain forests are now mainly confined to California,
Uruguay, East of China, Japan, south East Australia, Tasmania,
Newzealand and some small pockets (Fig. VIII. 17). Temperate forests
mostly have only two layers—a high tree canopy and a tree form
understorey (Fig. VIII. 17).
The productivity of such forest is high (Table VIII. 3) around 1 to
1.5 kg/sqm/yr. Here the temperature is lower than tropical rainforests. So
many of the common decomposers/such as earthworm are absent.
Consequently these forest floors are usually covered with thick leaf litter,
dry twigs etc. this is quite a contrast with tropical rainforest where
because of faster decomposition of litter, the forest floor is usually much
clearer.
c. A characteristic animal of these forests are the black bears (Ursus sp.)
in palaerctic and nearctic ones and in Australian zone (New Zealand) the
Kiwis—the flightless birds (Apteryx australis).
2.3 Temperate Deciduous Forests
a. In temperature regions where there is prolonged spell of cold (lower
than freezing), trees are deciduous i.e. their leaves fall off in winter. These
biomes however enjoy good rains. annual precipitation ranges between 2050". Weather, considering the latitudes of these forests, is relatively mild/
with real winter of about three months when the daily mean minimum is
around 0°C. Most plant forms here are hemicryptophytes (Fig. VIII. 18).
These are perennial plants of which upper parts die off in winter leaving
buds just above ground to germinate in early spring. Those bud remain
protected from frost by a thick layer of leaves which fall off from trees
in autumn. In fact the leaves just before falling from the trees in autumn,
take a beautiful reddish-brown hue rendering the same colour to the entire
deciduous forest belt. This is the famous ‘fall colour’. The Blue Ridge
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Orchid plant
Mango plant
Ginger plant
Mangoes
Annuals
(iv)
(o)
(i)
(ii)
(iii)
(v)
Seeds
Ginger
Fig. VIII.18 Classification of plants according to the positions of their
renewal organs (for explanation see text).
Mountains near Washington (capital of U.S.A.) looks picturesque with fall
colour during autumn. Here is a photo of fall colour in Virginia, U.S.A.
(Photo VIII. 1). The structure of temperature deciduous forest is rather
simple. It has two strata—the upper canopy of tall trees (50—100') and
the lower canopy of short trees (15—40') (Fig. VIII. 16).
Hopkin’s Bioclimatic
Law
b. The productivity of these forests ranges from 0.5 to 2.5 kg/sqm/yr.
Neither flora nor fauna is very diverse and the winter being rather long
(though may not remain below freezing for more than 3 months or so),
biological activities are confined mostly to spring and summer. Such
biomes remain mostly inactive during winter but spring to activity as soon
as spring arrives. Here a mention of Hopkin's Bioclimatic Law would be
worthwhile. Hopkins said that spring events occur about 4 days later per
degree of North latitude i.e. about 17 miles northward per calender day.
For instance if a temperate deciduous forest spreads about 250 miles
between its North and South ends the spring will come about 20 days
earlier in the South end than in the North end. Throughout summer the
biological activity gathers momentum reaching its peak just before fall
when all beings prepare to face winter. Plants prepare for their winterbuds and animals reserve food in their bodies to go into hibernation or
torpor.
c. At present temperate deciduous forests are mainly found in the Eastern
U.S.A., Europe—North of Alps till Scandinavia and Eastern Asia including
China. It seems much of such forests of Europe and Asia were
continuous before the last ice-age*. About 50 to 15 thousand years ago.
*Ice Age: During its geologic history earth has periodically undergone cooling and
warming. During cold phase the North polar ice cap expanded tremendously covering
most of Europe and North America and such areas. The cold age is called Ice Age. The
most recent ice- age abated about 10000 years ago. Change in temperature braught
changes in flora and fauna as well.
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Squirrels, Rabbits, Hedgehogs, Bears and Badgers are common
animals of American Temperate Forests. Japanese forests have a very
interesting denizen—Japanese macaque (Macaca fuscuta)—the only
species of monkey known to occupy such temperate deciduous forests.
2.4 Boreal Forests
a. These forests are in cool temperate regions (Map. VIII. 2)
characterised by chilly inhospitable climate. The word boreal has come
from the name of the Greek God Boreas—God of the North wind. Here
summer is very short and winter is very long—mostly covered with
snow. The dominant plants are conifers, spruce, fir and birch. Their
needle like evergreen leaves have better heat retentive capacity and the
conical shape of the trees help in shedding off snow more easily. The
boreal forests almost form a ring in the Northern hemisphere—spanning
North America, North Europe and North Asia. Southern hemisphere has
no such luxury—save a few scattered pockets such as Southern tip of
South America, South Patagonia and Tierra Del Fuego. The structure of
the boreal forest is rather simple—mostly conical shaped firs and birches
with one emergent upper storey and one under storey but no clear
demarcation between the two (Fig. VIII. 19).
b. Under snow cover of ground mosses grow providing food during
winter months, toherbivores like Caribou* and Moose** in North
America and Reindeer*** in North Europe. In Lappland of North Europe
a group of people—the Lapps live by hording only reindeers. The life and
cultures of Lapps are very interesting. There are four groups of in today's
world—a world of computers—who are still retaining their pastoral
culture. (1) Masais of Kenya (tend cattle); (2) Mongols of Mongolia (tend
horses); (3) Bedouins of Arabia (tend camels) and (4) Lapps of Lappland
(tend reindeers).
c. The Boreal Forests being mostly cold—long winter and short
summer—holds very few species of plants and animals. Hence the
productivity is low as well—ranging from 0.2 to 1.5 kg/sqm./yr. As the
productivity is low hence is the carrying capacity (explained earlier IV.
5.2). Here is an example. The Indian tigers need only 20 to 30 square
miles of forest per head but the Siberian tigers need more than 100 sq.
miles each. So whenever we plan to manage an ecosystem to protect some
species the carrying capacity of the ecosystem concerned needs to be
matched with the space requirement of that species in that ecosystem.
Most of the reserve forests of India suffer from this drawback. Some
animals however manage with extremely clever adaptations. Most birds
*Caribou (Rangifer tarandus)—reindeer of North America,
**Moose (Alces alces)—a large deer: the males have enormous palmate antlers
***Reindeer (Rangifer tarandus)—caribou of North Europe, both and have
antlers.
Nature of Boreal
Forests
Some pastorals of
To-day
Animals of Boreal
Forests
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a. Tropical Rain Forest
b. Temperate Rain Forest
Upper Canopy
c. Temperate Decidrous Forest
(share of Lake Isabella, Hamilton county,
ohio state, U.S.A.)–view from Boat House.
Drawn on the spot
Middle canopy
Bottom canopy
Weeds
Pebbles
d. Boreal Forest
Fig. VIII.19 The main storeys of different types of Forests.
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being fliers migrate southward to avoid winter cold (About this we have
written earlier (VI. 23 ). Beavers (Castor canadonsis), a member of rat
family which live in Canadian boreal forests have a fascinating way of
living. These live in colonies near stream in forested areas. They collect
twigs and when necessary cut down small trees by gnawing off their
bases and use these twigs and trees very ingenuously to dam up these
small streams. It is a wonder to see how big a dam these small animals
can construct this way. When the water level is high enough and so the
dam deep enough, they make a network of warrens in the shore, making
sure that the levels of warrens are higher than that of the top level of
water in the dam but the entrance into the warrens are always within the
dam and well under the level of water so that no enemy can reach them
unless they know swimming and also the locations of these under-water
entrances into the warrens (Fig. VIII. 20). Indeed beavers demonstrate
how resourceful and adaptive an animal can be in order to survive in a
harsh and competitive world.
d. Because the life is very harsh and inhospitable in boreal forests, variety
of animal species here are much fewer so the ‘web of life’ (i.e. the
number of species available as food to one another) is much simple and
short. One species may depend solely on the presence of another species.
So the density of one (i.e. no. per unit area) became dependant on
another. This leads to, in some cases, in regular oscillation of population.
For example, lynx and snowshoe hare in Northern Canada. The earlier
one is the predator and the latter one is the prey. This phenomenon has
already been discussed earlier in the chapter on Populations (Fig. VI.).
Beavers: Their
fascinating way
of life
Population
Oscillation
Warren of Beavers
Bed of the stream
Entrance into the warren
DAM made by beavers
Water in DAM
Water
Fig. VIII.20 Underwater entrance into the warren of beavers.
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2.5 Scrublands
a. Scrubland biomes are often formed where rainfall is rather low
(10—15" per year) and mostly concentrated within one short period and
temperature is usually high—more than 20°C in average. Naturally
productivity is also rather low and depending upon the exact amount of
precipitation and average temperature , and may range from as low as
0.05 to 0.75 kg/sqm./yr. Scrubland biomes are now found mainly in
Mediterranean, California, Chili, South Africa and south of Australia (Fig.
VIII. 21). Perhaps the semi-arid regions of Eastern Rajasthan, India, may
also be termed scrubland.
Plants and Animals
of Scrubland
b. In scrublands trees are mostly short, thorny perennials—such as ‘Jatti’
(Prosopis spicigera) in eastern Rajasthan the leaves and soft twigs of
which are used as fodder of camels. Some scrubland plants such as,
sagebrush of California are rich in volatile chemicals. Many plants here
are however are annuals or therophytes*. Scrublands are also fairly rich
in fauna. The famous predator puma or mountain lion (Felis concolor)
and the poisonous rattle snake (Crolatus viridis) and the jackrabbit (Lepus
alloni) etc. are found in Californian scrublands. Similarly scrublands of
Africa, Australia and India have their own interesting fauna. For example,
scrublands of Rajasthan, India still has—“blue cows” a species of
antelope. Locally these are called ‘nil gais’ as from a distance they appear
to have a bluish tinge in look.
2.6 Savanna Grass Lands
a. These are large tropical grass covered plains with scattered trees. The
rainfall is rather scanty (10-30" per year) and concentrated more during
summer months. Consequently the grasses of savanna have very deep
penetrating roots—around 6' or so. This help them to survive the long
dry season. Some of the trees of African savanna particularly the famous
baobob tree (VIII. 21) has a massive water holding trunk which can hold
up to 10,000 litres of water)! An wonderful adaptation indeed. Savannas
played a special role in human evolution. Is was in open savanna lands
where the ancestors of human beings who were tree dwelling apes, left
the tree and ventured out in the open. Here they learnt to walk erect and
developed skills for hunting in groups. The African savannas are really the
cradle of ecolution of today’s humanity.
b. Savannas occur in both sides of the tropics—in Africa, South America,
India, South East Asia and Northern Australia (Fig. VIII. 29). With their
wide expanses and easy visibility savannas are one of the most attractive
places on earth to visit and photograph. African savannas still hold such
splendid animals like elephants, lions, wildebeests, zebras, cheetahs and
*Therophytes—plants which are annuals and survive only as seeds
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Fig. VIII.21 A savanna landscape (in Afrika).
many species of deers. Many of us have been seen in TV those
wonderful films on wildlife of Africa and their annual migrations.
c. The productivities of the savanna grasslands are quite high—ranging
from 0.2 to 2.0 kg/sq.m./yr. Originally grasslands of vast expanses were
in all the continents. But unfortunately most of have yielded to the man's
need and greed and got replaced with agricultural fields or ranches (The
Oregon Trail. Francis Parkman 1966. Bantam Books). However thanks to
the early European settlers particularly the British administrators, the
remaining African savannas of today are amongst the best maintained
ones of the world. These abound with wildbeests, zebras, deers, lions,
cheetas, hyenas, eagles, elephants, giraffes and rhinos etc. Olduvai gorge
of Kenya/Tanzania is one of the most breath taking savannas of the
world. To be able to see the migration of wildbeests of Serengeti National
Park to Masai Mara of Tanzania is an experience of a lifetime. In dry
season when they move from one pasture to another, their movement is
spectacular. Huge trotting herds of more than 10,000 individuals are no
rarity. National Geographic Society (NGS) has rendered a singular service
in photographying these migraions and showing them through T.V.
throughout the world. NGS has helped to wake up men’s curiosity and
respect for Nature.
d. Grazing by herbivores in savannas is both orderly and beneficial. The
cycle of grazing begins with zebras who takes in the top layers only; This
Contribution of
British Biologests
and NGS
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Cycle of Grazing
and its Utility
is followed by wildbeests (also called gnus) who cut down the grass
swards further. Finally Thompson’s gazelles move in. These feed only on
the short grasses now exposed. In an experimental study where one area
is allowed to be grazed and the other area is not; the grassland of the
ungrazed area declined in quality and biomass. This shows normal grazing
by wildlife is healthy for an ecosystem and also for maintaining the fine
balance between fauna and flora.
Temperate
Grasslands
e. There are grasslands in temperate areas too. Both in South and North
America there are huge savannas abounding with ostriches and pumas in
south and and bisons and grizzly bears in north America. South American
savannas which are mostly in Argentina are called pampas. Charles
Darwin during his voyages with H.M.S. Beagle, 170 years ago, travelled
widely through Argentine pampas. With an escort of six gauches
(horsemen) Darwin took to the pampas and went exploring. They
(including Darwin) mainly lived off the land i.e. ostriches (called Rheas
now), ostriches’ eggs, armadillos and pumas etc. and whatever other
eatables they could lay their hands on.
f. Most of these beautiful savannas along with the resident native Indians
are all gone—sacrificed to give way to ranches of early European
colonialists. Here is a chilling description of the beginning of this process
by Charles Darwin.
Extermination of the
Indians
“Buenos Aires lay some 600 miles to the North, and all the intervening
plains- the Pampas—was unexplored territory over which tribes of
Indians (Patagonians) roamed and hunted. They were fierce and
aggressive people when aroused and great horsemen” ..................
...............” “But now they were fighting for their lives against the
Argentinians who wanted their lands in order to graze their expanding
herds of cattle; in fact it was the story of the America’s middle west all
ever again except that here the struggles were even more primitive and
more ruthless. The Indians were of course fighting a losing battle against
a war of extermination. .............................” Once there had been villages
of two or three thousands of them but by the time of Darwin’s visit the
tribes now mostly wandered homeless accross the Pampas: (Darwin and
the Beagle. Alan Moorehead, pp. 107—8, Penguin).
2.7 Tundra
Weather
Productivity
a. Tundra is the arctic grassland. In the Palaerctic region (North of
North America and North Eurasia) it covers a large area but in Neactic it
is confined only to the Southern tip of South America, Falklands and a
few small islands. In tundra the ground remains frozen throughout the
year save a few summer months. The average temperature however
varies considerably depending however whether the tundra is a oceanic*
*Oceanic—near a sea or ocean
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or continental* one. The tundras in West of Eurasia may have a winter
minimum of –10°C but the winter minimum of Alaska and Canada
(which are continental) may reach –30°C and in Northern Siberia –50°C!
Rainfall too varies from 6" to 12".
Ordinarily productivity is limited to the short summer of 60 days or
so.... Still when we remember the shortness of the period, the
productivity is fairly good ( 0.1 to 0.4 kg/sqm/yr).
b. The tundra ground is permafrost i.e. frozen throughout the year. Only
in the summer the top few inches melt lending it a slushy or muddy
appearance with puddles and shallow swamps here and there. The flora is
mostly arctic grassland—consisting mainly of lichens, some grasses,
sedges and a few dwarf woody plants. The perennials are generally
hemicryptophytes** and chaemophytes***. During summer when there is
liquid water in soil, tundra abounds with mosquitos and black flies whose
bites make living there in summer miserable. Other remarkable animals are
caribou, mask ex, arctic hare, arctic fox, lemmings, ptarmigan and some
migratory birds. While the mammals stay put during winter, (save caribou/
reindeer who migrate south), the birds migrate. Amongst the birds, while
the goose and the honkers are the most renowned migrants (as their
formation flights and honking is a common sight and noise autumn skies
of U.S.A.), it is the arctic terms (Sterna paradisaea) who have earned
most respect. These amazing birds nest during summer in arctic tundra
but migrate to antarctica during winter of arctic. This annual migration of
25000 miles makes these birds indeed the most remarkable flying machine
amongst animals.
c. Because of the preserving capacity of ice, tundra soil (which is
permafrost) holds fossils of some animals in a very well-preserved state.
Most famous of these fossils are mammoths. Mammoths (Mammuthus
primigenius) the ancestors of today's elephants, used to roam in Northern
temperate forests and tundras even in late Pleiostocene age—around 2015000 years ago. Because of low temperature, frequent snowing and
slow bacterial action, Siberian tundra still holds many mammoth-fossils in
extremely well-preserved state. The whole bodies of some are preserved
in ice with muscles, hide, fur and all. One such fossil is in Spitsberg
Museum of Russia. To-day fossil hunting in Siberian tundra is a big
business.
d. As the weather is very harsh (cold, freezing etc.), floral and faunal
diversity of tundra is low. This being so the food-chains of animals are
also very short. Many have only two or three species of prey as food. So
*Continental—deep within a continent with no ocean nearby.
**Hemicryptophytes—plants whose buds are just below the surface of the
ground.
***Chaemophytes—plants whose buds are near the ground.
Soil, Flora and
Fauna
Mammoth’s Fossils
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Population
Oscillation in Tundra
if the number of one goes down the predators’ number too will go down.
Following to this and owing to this, the prey population will rise very
fast. This will soon be followed by a rise in predator population.
consequently such rises and falls will go on in a cyclic pattern. Such
violent rises and falls in populations of prey andpredator is known as
Population oscillation. Such oscillations are of common occurance in
tundra ecosystems. Lemmings’ populations in tundra exhibit such
oscillations spread over a 4 year cycle (for more on ‘population
oscillation’ see chap. VI).
The Lemmings’
Suicide: Truth
behind it.
There are stories of Lemmings of Norway migrating en masse
towards the sea and finally jumping over the cliffs only to commit
suicide. But the truth is something else. In their 4-year cycle of
population oscillation when the population density of lemmings is at its
peak, these migrate in search of better pasture elsewhere. Norway being
full of fiords they find highways to migrate. But they are good swimmers.
So when faced with such situation these jump into the sea and swim
accorss to find new pastures. So Lemmings’ jump over the cliff is not
suicide but an endeavur to survive.
2.8. Deserts
Main Features of
Deserts
a. We began our presentation on terristrial biomes with tropical rainforests, we shall end this with the antithesis of that—the deserts. Tropical
rain forests are too wet, humid and warm while the deserts are too dry,
hot and at times cold. Lack of water is the dominant ecological factor in
deserts. Areas where annual rainfall ranges from 0-8" are called deserts or
arid regions; and areas with more rainfall as semi-arid regions. Central
Sahara is the absolute desert i.e. the area which receive no rainfall. During
daytime most deserts are either hot or very hot . Daytime air temperature
may reach 50°C and sand surface temperature 90°C ! Gobi of cenral Asia
however is a cold desert. The large deserts are mainly in Asia—Gobi and
Tibet, in Africa—Sahara and Namibia and in Australia—central Australia.
Deserts of North and South America are relatively small. Such small
deserts are many.
b. In deserts draught is the main restrictive factor for productivity; lower
the rainfall—lesser the productivity (Table VIII. 3). Many desert plants are
therophytes—passing the draught as seeds for months and then sprouting,
growing and flowering all within a few weeks after rains. Deserts look
beautiful then. The perennials which are mostly shrubs have very little
above-ground biomass but very extensive and deep underground root
systems. The productivity of above-ground biomass ranges only between
250 to 500 gm/sqm.yr. but of the underground one is much more,
reaching in some extreme cases to 24 kg/sqm/yr.
c. Considering their low precipitation and high drought, many deserts still
have a variety of plants and animals. Some plants as we said before,
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maintain a large amount of underground biomass while some others
convert the leaves into thorns—to reduce loss of water, and some
develop succulent trunks to store (e.g. cacti in Arizona deserts., Fig.
VIII. 22). Because of scarcity of resources particularly water, desert
plants, whereever they are tend to tend become spaced apart (Fig.
VI. 15). To achieve this these plants secrete some root hormones—
ectocrines which discourage growth of another plant near it (e.g.
Prosopis spicigera in Rajasthan, India).
d. Desert fauna also show characteristic adaptations. The integument of
desert insects is waterproofed by a coat of wax, reptiles all possess
waterproof skin armoured with scales and birds are helped by their
general higher body temperature (about 104°F) and a coat of feathers
which are highly insulative. Feathers are so good at insulation that that the
soft down feathers from the belly of eider ducks are used, instead of
cotton for pillows and quilts. Such pillows and quilts are very comfortable
for use in cold countries. Desert mammals too show various adaptations.
Many are nocturnal in habit and thus avoid the extreme heat and draught
of daytime. In night temperature falls but humidity rises. This diel
rhythm* (of humidity and temperature) helps desert animals to move
Fig. VIII.22 Canon cacti of arizona desert.
*Diel Rhythm: When a change in a biological activity becomes associated with
the change from day to night and vice versa, it is called a diel rhythm. For example,
vertical migration of flanktons—upwards during night and downwards during day, is a
diel rhythm.
Desert Plants
Desert Animals
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around and hunt in more favourable environments. The desert scorpions
which are large and very poisonous hunt only in night. There is another
large predator, a spider found in many West Asian deserts including
Western India. Amongst the desert mammals camels deserve special
mention. These are large animals who can travel long distances, without
drinking water carrying huge loads on their backs and for several days
(with night halts). Camels are so useful for survival to desert nomads that
they are popularly called ‘ships of desert’. Australians have introduced
camels into their country to exploit their deserts more profitably. Besides
camels, most desert vertebrates—mammals, reptiles etc. have developed
water-efficient urine producing mechanism. Some secrete urine in a very
concentrated form with little water in it while others completely recycle
the water and secrete in the form of solid white granules of uric acid (like
house lizards).
Beautiful Desert
Deserts with their wide expanse of rolling sand dunes and majestic
herds of camels striding along in a string on the top of sand dunes, do
lend a special attraction to any visitor who loves Nature.
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Chapter IX
Pollution
(Torturing the Nature)
Topics
IX.1. Introduction and Definition
IX.2. Types of Pollution
A. Chemical
B. Physical
C. Biological
D. Psychological
This page
intentionally left
blank
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CHAPTER IX
POLLUTION
(Torturing The Nature)
1. INTRODUCTION AND DEFINITION
1. By now we have acquired a broad idea about the basic principles
which guide the relationships of living beings with their environment and
vice versa. Also, we have a glimpse of the enormous varieties and breath
taking panoramas of different regions of our Mother Earth. She is verily
wrapped with a many splendoured robe. Here we see how either through
our ignorance or, through greed aided by modern technology or both, we
are tearing up this beautiful Earth’s robe into rags. One of the main
culprits for these damages is pollution. What pollution is and how is it
affecting the environment is the issue of this chapter.
2. What is pollution? Is some unwanted chemical in environment a
pollution? What about too much sound? Sound is not a chemical. Is
unwanted sound a pollution? When forests are cut down and as a
consequence river beds get silted up during monsoons, what is that—a
pollution? If a child’s mind is exposed to such things that, when adult he
becomes a criminal—shall we call such exposures pollution? When
political and social outlooks encourage one group of people to treat
another group as inferior or as enemies—what shall we call such
outlooks—pollutions? Pollution is a word which deserves a very wide
definition. It seems to us an appropriate definition of pollution could be as
follows. Any Interference with the Normal Rhythm of Nature Through
Human Intervention is Pollution. The agents for such initerference could
be many, a chemical agent such as DDT, a physical agent such as
radiation, or a cultural agent such as social upbringing and teaching. By
interference we generally mean some sort of detrimental intervention.
2. TYPES OF POLLUTION
1. Unfortunately however only such interferences are considered
pollutants which harm our interests. This is an anthropocentric definition
i.e. a definition which generally takes into account only man’s interest.
This should not be so. The interest of all species of living beings should
be taken into account. We all are children of God and interdependent.
Definition of
Pollution
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Fortunately, wise people all over the world are becoming aware about the
needs of other living beings and are initiating steps to protect them. This
is very laudable. In this endeavour the British, the Americans and the
Europeans are in forefront.
Pollution causing agents can be grouped into four broad categories.
A. CHEMICAL—such as DDT.; Alkyl mercury; Chlorofluorocarbons;
Smog; SO2; Crude oil; Radio active isotopes; Detergents; Dusts;
Fertilisers insecticides and; a host of other chemicals.
B. PHYSICAL—such as Noise; Heat; High Energy Radiations from
radio-active isotopes; Ultra-Violet ray; Ultra-Sonic sound etc.
Types of Pollution
C. BIOLOGICAL—such as explosive growth in number of any
species—plants or animals (including humans); Genetically
engineered species; and Disappearence of endemic species etc.
The explosive growth of a single species of living being—Home
sapiens is, we believe, the single most damaging polluting agent
today.
D. PSYCHOLOGICAL—such as various educational, social and
religious practices of man which result in developing a bias in the
minds of one group of human beings against another group.
Out of these four categories the last one we shall not deal with here as,
that constitutes the material of an entirely different type of book—
unrelated to the basic theme of this small book.
2.A. CHEMICAL POLLUTANTS
2.A.0. Now-a-days so many chemicals have been identified as polutants
and there are so many different techniques developed to measure them
that discussing them all, or even most of them, would be too much for the
aim and scope of this small book. Here we shall refer only to a few of the
most common chemical pollutants, how these are generated, what harms
these cause to our ecosystems and what should we do to reduce the use of
these. Here are some:
2.A.1. D.D.T.
2.A.1. The first one is Dichloro-diphenyl-tetrachloroethane, in short
DDT. DDT is a very powerful and very hard-to-destroy insecticide first
developed during Second World War. Initially it was extensively used
during war, against various insects in battle-fields to get rid of these from
the camps of Allied Soldiers. Then everybody was happy. Soon however
the negative sides of DDT. began to come into notice. Negative sides are
mainly two.
a: First, the acquirement of resistance to DDT. by insects which are
subjected to frequent DDT. spraying. This happens in this way. Every
time DDT. is sprayed—a few—only a few—of the insects sprayed, do
not die. These a few survivors are individually more vigorous and
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resistant to DDT. When these survivors reproduce they produce a slightly
more vigorous strain whose general level of DDT resistance is higher.
Now if these are again subjected to same dose of DDT spraying, there
will be more survivors than before. In this way, after several generations,
the DDT resistance ( or DDT tolerence) of these insects will be so high
that none of these will die if, DDT is sprayed at the same dose as before.
This is DDT resistance. This means as time passes one has to use a
higher and higher dose of DDT, to kill insects of same species. Soon
DDT spraying will be too costly. This is how Malaria Eradication
Programme of Govt. of India spearheaded by National Institute of
Communicable Diseases, New Delhi, although initially successful,
ultimately failed to eradicate malaria from India.
b: Secondly, persistence of toxicity of DDT (i.e. the poisonous
effect) may last as long as ten years. This is a very serious matter. During
this long period DDT travels from the target insects, through food chain
(for Food Chain see IV) and soil to human bodies and others such as sea
birds. There owing to biological magnification (for biological
Magnification see V. 3) DDT becomes lodged in a much higher
concentration. In some cases DDT concentration in milk is so high that it
is positively harmful (Table V. 3). Now about the sea birds. Through foodchain and rainwater most of the DDT sprayed for crop protection finds its
way to the sea. From sea again through food chain, DDT climbs up into
the bodies of sea birds. In sea-birds' bodies DDT concentration reaches so
high level that such birds lay very thin-shelled eggs which break easily
when the birds try to sit upon them for incubation. This egg-failure
reached so high proportion that the populations of some sea birds declined
alarmingly. The national bird of U.S.A. — bald eagle (Haliacetus
bucocephalus) almost faced extinction. Now owing to timely vigorous
measures their number is rising.
c: Rachel Carson (1907-64) An American Marine Biologist from
Woods Hole Marine Biological Station and Johns Hopkins University,
who with her love for nature, knowledge, wisdom and grim determination
first brought to light this lethal link of DDT with the alarming decline of
sea-birds' populations. As expected her discovery was not easily accepted.
Interests of the producers of insecticides were involved. But ultimately she
won. She has written two remarkable books on such matter—(1) Silent
Spring (1962. Houghton Mifflin, Boston), (2) The Sea Around Us (1952.
Oxford University Press). Besides these she wrote many valuable
technical papers on this issue. Ultimately due to her persistent lobbying
U.S. Govt. banned the use of DDT—the first country to do so.
d: Before we move to other pollutants here we would like to
introduce briefly, some important concepts about the use of insecticides/
drugs etc. The first concept is Lethal Dose 50% or LD-50. The amount
of insecticide (or any other poison) which is required to kill 50% of the
insect population (or any other pest population) which is the target of the
Rachel Carson
(1907-64)
LD-50
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Chemicals in
Nature
insecticide, is called lethal dose 50% of LD-50. This is shown in Figure
IX. 1. where the mortality (of the target population) is plotted against the
dose in a graph. From such graphs based on laboratory experiments dose
for LD-50 of an insecticide etc. are determined and recommended to
farmers for their use. There is a presumption behind recommending LD50 as field dose. The surviving population after recurring LD-50 uses will
no longer be able to do any appreciable damage. Otherwise they would
have to recommend a much higher dose to ensure LD-100 or 100% kill.
This would have become too costly to be practical. The second concept
is Drug-Fastness or Drug-Resistance (see earlier in this chapter). This
use of LD-50% for agricultural purpose however has an inherent hazard.
Some offsprings of the population surviving LD-50, is likely to have a
resistance level slightly higher than the parent stock. In this way, after a
few generations this pest will be resistant to this insecticide if applied at
this dose. This acquirement of resistance of an insect to an insecticide
when treated with the same insecticide over generations, is called drugresistance or drug fastness. The third concept is the Persistence of
Chemicals in Nature. The problem with applying chemicals in field is
the long time which some of these chemicals take to be broken down into
simpler and harmless components. This is called persistence of toxicity
of a drug/chemical in nature. For DDT it is ten years or so. During this
long time this chemical passes through the bodies of many other harmless
and useful species of living beings (through food-chain), which were not
its targets, and become increasingly concentrated into the bodies of these
creatures and ultimately cause their death—a most unforseen and
unwanted consequence—some of such unfortunate creatures are bees and
70
Mortality %
Persistence of
Toxicity of Drug
Ecology for Millions
50
50 %
mortality
(or LD50)
30
10
10
20
30
40
50
60
Dose (gm. sq-m-/hr.)
70
Figure IX.1 Lethal Dose 50% (or LD50)
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wasps. Bees pollinate flowers and wasps iradicate insect—pests by eating
their larvae. This is what happened with sea-birds which was first shown
by Rachel Carson. (Recently there was a news item in the Bengal daily
‘Bartaman’, Oct/Nov. 2001, that the vulture population of West Bengal
(INDIA) has gone down remarkably. It seems to us perhaps the vultures
of West Bengal are also suffering like sea birds). Most of the carcasses
they eat might have too much of DDT in them.
2.A.2 CO 2 ( Carbon dioxide) is another common pollutant. CO2 is
released into air when we burn wood or any product of wood such as coal
or oil. Therefore with increasing industrialisation all over the world, CO2
production is steadily rising. Hence more and more CO2 is being released
into atmosphere. This is hapening with an increasing rate, since the
beginning of industrialisation i.e. for the last two hundred years or more.
Also CO2 is a normal constituent of air (0.03%). It has been discussed
and shown earlier (Chap. V) that within past 20 years (1960-80) CO 2
concentration of air has increased about 7%, of 0.03% (Fig. V.8).
a: CO 2 however has a special property. It allows sunlight to pass
through it easily and while doing so absorbs heat (infra red radiation) both
from sunlight as well from earth's surface. So higher concentration of CO2
in air tends to warm up the atmosphere faster. The same thing happens
with a greenhouse. (A greenhouse is a glass enclosed room in which coldsuceptible plants are grown). The glass cover of greenhouse allows the
sunlight and heat to pass into it easily but retards their escape readily. So
a greenhouse remains relatively warm in winter). Just as the glass cover
keeps the greenhouse warm so does the CO2 content of atmosphere. It
keeps the atmosphere relatively warm. This phenomenon is known as the
Green House Effect of CO 2 on atmosphere. This is exactly what is
happening now. During the last 100 years or so, as the CO2 content of
atmosphere is slowly risesing (Figure V.8 ), the average temperature of
earth’s atmosphere has also risen. It has risen by 1/2°C. This has resulted
in severe drought in some places (ex. Sahel areas in west-south of Africa
(and devastating cycones elsewhere (ex. El Nino, Mitch) and melting of
some of the heretofore permanent polar ice chelves. Only recently one
huge permanent iceberg (of several hundred square miles) has split out
from antarctic ice shelf and started floating away and melting.* People are
worried. Sea level may rise worldwide.
*On March 17, 2000, through satellite they found a very unusual thing. A huge
chunk of ice, about 200 mile long, 25 mile wide and 800 feet thick, broke out from
the Ross Ice Shelf of Ross Sea. They named it B-15. Slowly it splintered into smaller
bergs, floating around the Ross sea and melting. At first B-15 was 1900 square miles
in area. The Antarctic Peninsula has warmed about 4 degrees in the past 50 years.
“The winter sea and area has been so reduced in recent years that krill populations—
which feed on algae that initially grew in the ice—are in danger of crashing. As krill are
the basis of almost the entire Antarctic food web, seal, whale and penguin populations
could follow.” (N.G.S. December 2001).
2.A.2. CO2
Green House Effect
Hazards of Green
House Effect: Is it
serious?
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b. This seems to us however a rise in CO 2 content will induce
increased photosynthesis and that in turn will ultimately take care of extra
CO2 in atmosphere. At any rate our Mother Earth has already passed
through four ice ages - Grand Canyon, Lauramide, Cascadian and
Appalatian - the last one being only 15 to 20 years back. During
Appalatian half of Europe was under ice and North Afrika cool and
forested. That was the time when the cave dwellers of Altamira (Spain)
drew those excuisite cave paintings of bison hunt. (Fig. VII. 6).
2.A.3. As2O3
Arsenic poisoning in
Rajasthan Villages
Arsenic poisoning in
West Bengal
Villages
2.A.3. As2O3 (Arsenic Oxide), is a harmful salt found in deeper layers of
soil—in rocks. This chemical dissolves in water and tends to seep into
the upper layers of soil. In this way it contaminates the waters of some
wells. In semi-arid places such as Rajasthan of India people draw water
from wells—oftern 125 feet or more deep. Such waters are frequently
found contaminated with arsenic and other harmful salts which seep into
the well. That is why people from some vilages of Rajasthan, India, suffer
from arsenic poisoning. Unknowingly they use such waters for drinking as
well. Interestingly it is noticed that the rich people of the affected villages“banias” (businessmen) and “thakurs” (land holders) do not suffer from
arsenic poisoning. Such people live in brick /stone houses with flat roofs
and paved courtyards. Rainwaters from roofs and courtyards of these
houses are not allowed to seep into the soil but all are channelled into
large brick reservoirs. The houseowners use this stored rainwater solely
for drinking, throughout the year. So they escape arsenic poisoning. The
remaining villagers however who have to use well-water for drinking
often suffer from arsenic poisoning (also pl. see II. 3.2.(C)).
a: Recently arsenic poisoning is reported from some villages of West
Bengal, India as well. This was not so earlier. It seems the reason lies in
the recent disturbance of its ecosystem. Earlier when Bengal (of India
before 1947) was well forested adequate rainwater could enter into the
soil due to sponge effect of the forest floors and also through many
swamps and ponds. Forests, swamps and ponds were much more
extensive and numerous then than now. Thus rainwater entering the soil
would leach down the arsenic into the deeper layers of it. So the upper
layers from which drinking water was drawn remained relatively free of
arsenic. Nowadays, in many places, trees have been cut down for
agriculture and swamps and ponds have been drained off to make way
for housing complexes. Consequently monsoon waters, instead of
entering the soil and reacharging the aquifers, quickly run off into the
rivers. Along with monsoon water a lot of top-soil also finds its way into
the rivers raising their beds. (Also see. II.3.2).
b: Two ills result from all these—first, arsenic seeps up from the
lower levels to the upper levels contaminating the wells and secondly, the
raising of river beds cause extensive and frequent floods during
monsoons. Annual monsoon floods are much more extensive and severe
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today than 25 years before. Recently, a local fortnightly (“Laban Hrad
Sangbad”, Dec. 19, 2001), has reported as follows. A comparison
between 22 years prior to 1964 and since 1964 shows that the drought
during the latter 22 years is 9 times more than during the earlier 22 years.
We now know that drought is partly caused by lack of ground water. We
also know that deforestation, draining off of swamps, filling the ponds are
are the main causes for inadequate recharging of groundwater. It seems
(according to the above report) in India alone, every year 1.5 million
hectar of forest are being cleared to meet the demands of the exploding
human population. If true it is horrendous. I hope it is not so or the Govt.
would wake up and do something to halt population growth.
c: Thoughtless deforestation is an ecological disaster. We are afraid,
the full significance of this damage, neither the planners nor the general
populace are aware of. Afforestation, water management and family
planning (to reduce pressure on land) all these three need be attended to
on war footing.
2.A.4. Ozone (O3) is a gas present in trace amount in our atmosphere.
However it stays mostly as thin film in the upper layers of our atmosphere
—stratosphere, 10 to 30 miles from the earth surface. Sitting over there
like a thin protective blanket it protects us by cutting off most of ultra
violet light (of solar rays) which is harmful to living beings. Unfortunately
nowadays the gas used extensively for refrigeration in most of the
countries of the world is chloro-fluoro-carbon (C.F.C.). This gas when
leaks out interacts with ozone and destroys it, thus creating gaps in the
protective ozone coat of earth’s atmosphere. Through those gaps the U.V.
rays of solar radiation hit the earth’s surface at much higher intensity
than elsewhere and harm the living beings thus exposed. Such gaps are
called Ozone-Holes.
2.A.4. Ozone layer
and ozone holes
4.a. Ecologists have already noticed signs of damage in the
ecosystems of some parts of the earth owing to over exposure to U.V.
rays. This and other consequences of overexposure to various other
pollutants have been discussed by ecologists and planners who gathered
from all over the world in recent International Ecological Conferences in
Brazil, Japan and South Afrika.* The participating countries including
India, have signed a resolution outlining what they would do, in a phased
manner to reducing pollution of biosphere. But none have stressed upon
population control which is the most basic issue.
Ecological
Conference in
Brazil
2.A.5. Smoke is a suspension of fine particles of carbon in air. Burning
of materials such as coal, oil, wood or wood products all produce smoke
and ash. Smoke pollutes the air of cities particularly where there are too
many cars such as Delhi. In winter smoke and fog together form smog.
2.A.5. Smoke and
Smog
*(INTECOL in Rio de Janeiro (1992), on Global Warming in Kyoto (1997) and
Earth Sumit in Johannesburg (2002).
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Smog is extremely harmful to lungs. A few years ago the senior citizens
of London suffered from heavy mortality owing to lingering dense smog
in winter. Improvement in emission control of automobiles is vital to
solving this menace. Many countries, including Indias are now taking
steps to reduce emission from cars.
2.A.6. SO2 and
other air-borne
pollutants
2.A.7. Land-Fills
2.A.6. Sulphur dioxide (SO2) and many other air-borne pollutants which
result from industrial and mining activities are very harmful to plants.
Lichens—a type of delicate plants* have almost vanished from
neighbourhoods of most cities and mining areas owing to SO2 and other
air borne pollutants. The naked hills around Queenstown, Tasmaina, stand
as mute witness of the ravages of sulfur fumes. SO 2 fumes from a
nearby copper mine has completely denuded an once-densely-forested area
spread over several square miles in Tasmania. To-day the bare grounds
stand purple with sulfur fumes a mute evidence of torture to nature.
2.A.7. A growing city mostly faces acute land shortage. So now-a-days
many city planners are using city garbage to fill up the surrounding
swamps and ponds etc. and thus create land for housing-complexes,
parks and roads. This is happening all over the world. Bombay and
Kolkata are doing this extensively. In fact some city-planners look upon
swamps and ponds as manna for them.
Recently however, ecologists have started worrying about this
method. First, dangerous chemicals are getting into the ground through
land fills which will very likely contaminate ground water and cause health
problems for long time to come. The other immediate problem that
worries us is the sealing off of the entry points of rain water into ground
to recharge the aquifers (the water bearing strata of the ground). Sooner
or later the ground-water-level will go down and then the trees too will be
affected. Recently in U.S.A. they have raised serious doubts on the
propriety of such land-fills (Washington Post 2004).
2.B. PHYSICAL POLLUTANTS
1. Radio-active Isotopes
So far we had been discussing of chemical pollutants which harm
through their interferences with the normal biochemistry of living bodies.
Now we shall discuss about physical pollutants which harm living beings
by the entry of, either high energy radiations emitted by radio-active
substances or, extra-ordinary mechanical disturbances generated by
external agencies such a sound, heat etc. Radio-active Isotopes (RAI) top
this list.
*Lichen: A group of plants whose bodies are made of symbiotic combination of
algae and fungi. These are found in rural and forest environments as light-green crusts
on rocks and tree-trunks.
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a. RAIs are the most dangerous of all physical pollutants. An isotope
is one of the two or more forms of an element which has the same
atomic number i.e. the same number of protons but different atomic
weight i.e. different number of neutrons. For example, the element carbon
which is an essential constituent of most biomolecules, has an atomic
number of 6 but atomic weight of 12.*
229
2.B.1. Radio-Active
Isotopes
But there is an isotope of carbon which has an atomic weight of 14. This
C 14 is a radio-active isotope of carbon. This radio-active carbon
automatically emits high energy radiations which are harmful to living
beings. Similarly there are isotopes of many other elements. Some of such
isotopes automatically produce high energy radiations such as alpha, beta
and gamma.
b. Radio-active-isotopes or RAIs automatically and continuously
produce alpha, beta and gamma radiations (generally symbolised as α, β
and γ rays). Of these beta and gamma are extremely high-energy
radiations hence when these enter into the bodies of organism,
occassionally these remove electrons from some atoms and attach these
free electrons to other atoms. In this way such radiations produce positive
and negative ion pairs and so these high energy radiations are known as
ionising radiatons. Ionising radiations are the chief causes of injury to
organisms from RAIs.
c. Generally radiation-damage to the tissues and organisms is
proportional to the number ion-pairs produced within the irradiated tissue
in an unit of time. Again the capability of producing ion-pairs is dependant
on the energy of these rays. Alpha and beta rays are corpuscular (i.e.
particles) but the gamma rays are electro-magnetic waves (related to Xrays). Alpha particles are parts of Helium atoms and hence huge in
atomic scale. These can travel only a few centimeters from the source
and can easily be stopped, even by a sheet of paper. Beta particles are
high speed electron beams and can travel several feet in air or penetrate a
few centimeters in the tissue. In contrast to these two, the gamma rays
are extremely high energy electro magnetic rays which can travel long
distances in air or tissue producing ionisations throughout their path.
Gamma rays can even go through thin concrete walls. So of these types
of radiations, alpha particls cause least and gamma the most damages to
the tissues.
d. Some elements go on continually emitting high energy radiations.
For instance Radium (Ra), Uranium (U), Plutonium (Pu) etc. For some
*Atomic Number and Atomic Weights of elements are shown in this way.
Atomic number is written above the abbreviated form of element and the atomic weight
under.
6
Thus Hydrogen = H11 ; Carbon = C12
; and Cobalt = CO 27
59 .
6
and CO 27
The radio active element of these isotopes are H13 ; C14
60
The cause of harm
from Radio-Active
Isotopes
The ionising capability of alpha, beta
and gamma rays
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Damages from
Radiation
others the common forms do not emit high energy radiations but some of
their isotopes do such as Hydrogen (H), Carbon (C), and Cobalt (Co).
There are many such elements which have radio active isotopes.
Radiations from such RAIs (mainly beta and gamma) cause ionisations
within the protoplasm. Such ionisations may lead to mutations (explained
later in this chapter), cancer and death. However it should be remembered
that cancer is also found in people who are not exposed to any known
source of ionisation. Exposure to some chemicals such as coal tar has
been found to cause cancer. With passage of time, other carcinogenic
agents (cancer causig) are being identified. To day cancer is a high
priority research area all over the world. A break through in this area will
sure be a Nobel Winning work. Exposure to high doses of radiation from
RAIs is extremely dangerous to life. The first known victim from
radiation is Madam Curie herself—the discoverer of radium. Unknowingly
she received a fatal dose of radiation while handling radium. She
developed blood-cancer or leukemia and succumbed to it. Later many
more have died. Measurement of doses or radiation to which a living
being may be exposed to without harm is although important to many but
somewhat technical and outside the scope of the small book.
Mutation and H.J.
Muller
e. These high energy particles and waves particularly beta (β) and
gamma (γ), destroy some body cells (somatic cells) and our gonadic cells
(germ cells). That is why when X-raying a patient, doctors keep the
testicular or ovarian parts of the body covered with a thick lead sheet
through which X-ray can’t pass. When extensive damages of body cells
take place—owing to radiation, the patient, after stages of illness, dies. If
however, the gonadic cells (germ cells) get damaged, the being may
produce offsprings with unexpected features—mostly bad. These
deviations are called mutations. Prof. H.J. Muller 1947 first demonstrated
that X-ray irradiation can alter genetic material leading to permanent
changes in the offsprings. Such changes owing to irradiation are
permanent and hence called mutations. Prof. Muller's discovery was such
a break through in the growth of knowledge of Genetics that he was
awarded Nobel Prize for this.
Danger from Atom
Bombs
f. None of these high energy rays are visible. So RIAs like Cobalt60 or
Uranium238 etc. are like invisible killers. Atom bombs not only kill thousands
of people directly (as at Hiroshima and Nagasaki) but also releases in the
form of ‘fall-out’ a variety of RAIs such as Cobalt60 and others which
retain their lethal property for years. In fact some retain their lethal
property for thousands of years. Half-Life of Carbon14 is 5568 years and of
Cobalt60 5.27 years. (Half-Life is the time required by a radio active isotope
to lose 50% of its original radioactivity.). That is why world is now trying
to ban the production and use of such horrible weapons as atom bombs.
g. There are other RAIs which may be injected into the ecosystems
from sources other than atom bombs. Nuclear Power Stations are very
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prominent examples of sources of RAIs These power stations are
sprouting up all over the world like mushrooms and more so in the so
called developed countries. Some of their by products are RAIs. These
have to be stowed away extremely carefuly, in safe and sealed containers
and placed deep inside the earth or sea-bed till their radio-activities come
down to harmless levels. This is the practice now but nobody is too sure
about the reliability of these measures as time required to check these is to
long and none of us will remain alive then. (Recently in N G S. July
2002, issue there is a very important article on storage facilities in U.S.A.
for RA wastes from Nuclear Power Plants).
Hazards of Atomic
Power Plants
h. Sometimes due to human errors, the radio-active fuel rods in a
nuclear power station, which normally generates heat in a controlled way
to produce steam in boilers for power generation, may become
uncontrollable. Consequently all on a sudden so much of heat is generated
that the entire power plant may explode with all the horrible consequences
folowing swiftly. Such accidents are however very rare. Still recently one
did happen at Chernobyl, U.S.S.R. (Year 1986). It was a terrible disaster.
Thousands have died. After the accident the Russians have sealed up the
whole power plant with thick concrete shroud. Several hundred square
miles of land around Chernobyl have the banned for human habitation. (So
dangerously high was the level of radiation—mainly rays, that a Russian
helicopter pilot sent several days after the explosion, to survey the extent
of damage from his helicopter, whose floor was covered with a thick
lead sheet (to protect him from beta and gamma rays) nowithstanding,
received so heavy dose of radiation that after a few months, he developed
leukemia—blood cancer, and died. He could not be saved although some
American pilots and doctors tried to save him through bone marrow
transplantation. The explosion of the atomic power plant at Chernobyl is
comparable with a nuclear volcano that has erupted. From that angle all
nuclear plants are inherently very very risky.
The Chernobyl
Accident
Atomic power plants need constant vigil and monitoring. With them
nothing should be left to chances. The first atomic power plant of the
world is that of Windscale of U.K. Now they have several all over the
world. So far India has two—one at Trombay near Mumbai and another
at Kalpakkam near Chennai. Recently they are planning to erect one more
in India at Sundarbans—the only mangrove ecosystem of India and
perhaps the only reserve forest in India with a reasonable number of
tigers. To destroy Sundarbans would be an ecological disaster and not
having tigers would be a matter of great loss and shame for all Indians.
Ecologically and ethically this is very very wrong. Tigers too have a right
to live. Also, mangroves ecosystem of Ganga delta is too precious to be
trifled away. If mangroves of Sunderbans is gone the survival of entire
Ganga delta will be threatened. Putting a Atomic Power Plant in
Sunderbans will be an ecological folly of gargantuan proportion. Tigers
will vanish. The very existence of Haldia and Kolkata will be at stake.
Atomic Power Plant
in Sunderban-a
dangerous idea
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Prawn culture will be destroyed. Mangroves will go, and soil erosion will
assume dangerous proportion. Hilsa fish will almost vanish and many
more irreversible ills will follow. Then no amount of ‘Foreign Aid’ will be
able save Sunderban and West Bengal from calamities. Desire to employ
“higher Technology” without carefully assessing the price for it is indeed
a very wrong way of planning. People in power, if they really love India
should desist from doing this. Ambition with little knowledge is a
dangerous thing. If an atomic plant is erected there one of India's few
proud possessions will be gone forever.
Solar Power station
in Rajasthan Desert
k. Besides it is time now we start working for solar power, wind
power and tidal power and no more for thermal plants or atomic plants.
Rajasthan desert is a huge untapped source of clean power. It is time we
turn our attention to such sources of power. If we can only tap 1% of
solar energy for power generation India will be flooded with power.
2.B.2. SOUND
2.B.2. Sound
Sounds in animal
world
Sometimes noise may be a source of pollution. Too much noise is
positively harmful to hearing and health. People who are constantly
exposed to too much noise of machines as, pneumatic drils, railway
engine whistle, aircrafts, pneumatic horns, crackers, mikes etc. (without
adequate protection to ears) sooner or later, all suffer from impaired
hearing. Some may even become deaf. A new-born baby's hearing may
suffer permanently. Too much sound may disturb sleep and thus cause
health and healing problems. Human beings can hear sound form 60 to 75
decibel (an unit of sound). But sounds above 70 decibels are harmful to
hearing.
a. Many animals can produce, hear and communicate through such
sounds (ultra and infra sounds) which we can’t hear. Such animals are
bats, elephants, porpoises and whales. There may be many more such
animals endowed with such capabilities. Recently it has been proved even
ants when in pain scream.
b. It is extremely important therefore that, the permissible level of
sound production near human dwellings and public places be determined
and enforced. This is an area where more information are urgently
required. These however can be easily found out through simple
laboratory experiments. People of Europe, North America and other rich
countries are fairly conscious about the pernicious effect of too much
sound so, they have strict laws regarding permissible range of sound
production in public places. Unfortunately in India and such
underdeveloped countries such awareness is far from adequate. Only
recently some courts of India have ordered to keep the sound level in
public places within 65-70 decibels.
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2.B.3. HEAT
Our universe has a very wide range of heat starting from 10,000°C on the
surface of the sun to minus 100°C or less in polar ice caps and some
planets. Life however can exist only within fraction of this vast
temperature scale that exists in this solar system (Fig. III. 6). This small
range is approximately from + 90°C or so to – 60°C or so i.e. a span of
only 150°C. Of this 150°C any individual species can tolerate a still
smaller range say, around 30°C. Protoplasm (the semi-liquid content of a
cell) of an individual species however cannot tolerate any temperature
fluctuation—it can stay alive only at a fixed temperature such as of birds
and mammals or with very little fluctuations of temperature such as of
fishes, amphibians and reptiles. To survive in an habitat with fluctuating
temperatures, a species develops various adaptations—some structural,
some physiological and some behavioural. For details pl. see III.
a. When the ambient temperature of a habitat or a breeding place
changes, due to pollution, the population of the species concerned, suffers
severely. For instance the population of salmon fish drops if the
temperature of their breeding grounds namely, pools in the rock streams in
cold mountains, rises owing to deforestation. (Also the turbidity matters.
Cool and clean water in their breeding grounds is a must for salmons and
eels.)
2.B.3. Heat
Pollution: Temperature of Habitat
b. The toleration range of a species depends upon the ecosystem
it lives in i.e. its niche. For instance a yak (a variety of cow) which lives
in Tibetan plains, can live only in cold climate (say –10°C to +15°C)—
alpine climate*; Similarly a good cow from northern plains of India say a
Haryana cow prefers warm and dry climate of western India (Say 5°C to
30°C). Again, the different stages of the life—cycle of an animal or plant,
may require even a still narrower band of temperature to survive and grow.
Here are two examples—one a fish (Salmon—Salmo fario) and another
an insect (Silk worm—Bombyx mori).
c. The famous commercial fish salmon spends most of its life in
seas but for laying eggs it must swim up the rivers in the colder regions
of the earth, all the way to nearly the source of the river and lay eggs in
cold clear water pools. If these waters are not so cold or turbid spawning
will suffer and consequently there will be crash in the salmon population
of the seas. So a good catch of salmon during fishing season in seas may
very well depend upon, among other things, the coolness and clearness
of the waters of the breeding grounds of mountain rivers.
d. Now the silk worm. The Chinese silk worm lays its eggs in
Autumn. These eggs do not hatch immediately. Instead those will enter
into a winter phase—a dormant phase—technically known as diapause. In
*Alpine Climate : Pl. refer to ‘Terrestrial Ecology’ in Chapter VIII.
Spawning of Salmon
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Worms
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early spring, after undergoing diapause development the eggs will hatch
and then the normal larval activity will be resumed i.e. feeding, moulting
etc. Undergoing diapause in winter is a compulsory requirement for the
eggs of Chinese silk worms. If for some reason or other, the period of
exposure and intensity of cold the diapausing eggs are subjected to are
different from the normal, the silkworm population will suffer. Pollution of
the native environment, owing to human interference sometimes causes
such situations.
e. Thus although as a physical factor temperature is vital but pollution
may adversely affect temperature and thus cause catastrophic rise or fall
of a population. The same is true for other physical factors. for instance,
dust may diminish sunlight and effect photosynthesis.
2.B.4. MOISTURE
2.B.4. Moisture
The river Ganga of
India and its
Pollution
Not only liquid water is a must for the sustenance of life, the nature of
liquid water, as well as relative humidity (i.e. percentage of water vapour
in air), are also crucial for living beings particularly animals. Those
animals who live in fresh water all face one comon challenge—too much
water tend to enter into their bodies through endosmosis and those who
live in salt water face the reverse situation i.e. too little water tend to stay
into their bodies due to exosmosis. Again, those animals who live in land
other than deserts, face a variety of other challenges regarding relative
humidity, according to their niches and character of their skin
(integument). Thus a toad whose skin can't stop evaporation of water
through it, can move about only during monsoon season when the air is
humid. During dry season toads hide within burrows. So anything that
drastically changes the quality of water or relative humidity of a place
damages the local ecosystem. Also human activities, at times, adversely
affect ecosystems. For instance, release of warm waters into the rivers
from nearby factories and power plants etc. damages the river ecosystem.
The river Ganga of India is a victim of triple pollution—heavy silting due
to deforestation and agriculture in her watershed secondly, the pouring of
factory affluents and city sewage and the third cause is a religious
practice of Hindus. Many Hindus believe that if, after death, their bodies
are burnt on the banks of Ganga their soul will go to heaven. So after
cremation the ashes and other related items all are thrown into Ganga. Today the water of river Ganga is heavily polluted. These are adversely
affecting the fish population as well as the mangrove ecosystem of
Sunderbans in the mouth of Ganga.
The other instance is the 900 miles long canal that has recently been taken
from Ganga into the Ganganagar district of Rajasthan. This has increased
the moisture content of the soil and the relative humidity (R.H.) of air of
that district. The ecological effect of this on the erstwhile local ecosystem
though not yet fully known, but is very likely to be considerable. The fate
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of other Indian rivers are scarcely better. Unbriddled rise in human
population coupled with public and Govt. apathy towards maintaining the
health or river ecosystems are slowly choking the Indian rivers. Indian
rivers urgently need health care, but little actual works are being done.
Most are ad hoc steps.
2.C. BIOLOGICAL POLLUTANTS
So far we had been discussing only about various chemical and physical
agents which disturb the rhythm of Nature and the consequences that stem
from such disturbances. There is however another type of pollution which
essentially concerns with the characteristics of populations. So the effects
are not so obvious in the initial stages. Generally a healthy natural
ecosystem remains more or less self—supporting and stable for hundreds
of years and the various populations that inhabit it remain unchanged. (In
the long run however, nothing is unchanging otherwise evolution would
not have taken place). In fact the stability of the sizes of componentpopulations is a basic feature of a healthy self-sustaining ecosystem. Now,
if through human interventions the polulations of one species is
suppressed or encouraged, the result will be the near elimination of one
species or explosion of another or both.
2.C. Biological
Pollutants
a. Here is a case where suppression of one has resulted in the
explosion another. In the Virginia State of U.S.A. they have several reserve
forests. In these hunting of deers is prohibited and also they have
eliminated the natural enemy of deers i.e. cougars (Felis concolor) from
these forests. Populationwise for deers the signal is green and for cougars
red. Soon the deer population exploded. So to keep the forests from being
overgrazed by deers and the road safe to motorists, every year the Forest
Department of Virginia declares a few days as open season for deer
shooting. Around 50,000 deers are shot down every year in Virginia State
alone. This is a clear case of population explosion owing to the removal
of predators. Thus predators help to keep the forests healthy. (Similar
situations can be identified from the relative population changes of animals
and plants of different countries). More have been written on this earlier
(V. 3.7).
Explosion of deer
Population in Virginia
U.S.A.
b. Another case is human beings (Homo sapiens). Man owing to
their superior intellect (thinking, remembering, communication capability
and of using tools etc.), since their beginning, had been a negative
influence on their environments. Wherever man settled in large numbers,
the number of other organisms whether plants or animals, got severely
depleted. Lions (Felis leo) who were endemic throughout north and east
Afrika and western Asia including India, have been eliminated from most
of these places. In fact these regal animals were so common in western
India that emperor Asoke used their regal look to adorn the heads of the
beautiful pillars he erected in many places of his empire. Now these regal
Lions and Whales
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animals are confined only in a few states of Afrika and a small reserve
forest in India (Gir forest). Whales, the beautiful and majestic animals of
seas were almost going to be hunted out from the surface of mother
Earth but for the timely, intervention of International Whaling Commission.
Today their numbers are again rising.
c. The industrial Revolution of 16th century, a product of modern
science, gave Europeans knowledge as to how to obtain fossil fuels and
use these as sources of heat and power. Armed these twin tools—modern
science and power from fossil fuels, Europeans began to exploit
ecosystems of the entire world solely for their own benefit. The vast
continents of North and South America were discovered and, found
thousands and thousands of square miles of land there just lying open to
be occupied and exploited. Soon the populations of immigrants from
Europe to these continents, particularly from Gr. Britain, Spain, Portugal,
France, Italy, Germany, Denmark, Holland and Norway and others—
mainly the sea-faring nations, exploded. They occupied and colonised
entirely North Americal, South America, Australia and New Zealand and
partially the coastal belt of Africa. The relatively unresisting and small
populations indigenous people of these countries were mostly decimated.
(pl. see Table I. 1).
d. This was a population explosion of the Europeans in a grand scale
at the cost of other populations, just as lions were eliminated from most
of Africa by the burgeoning human populations in that area. At that time
most of European colonies to North and South Americas had very large
families averaging six to ten children in each. Soon after that pristine
ecosystems of North and South Americas began to suffer. Passenger
pegions are completely eleminated. Bisons came to the brink of
decimation. Bald Eagle’s populations dropped to dangerously low levels*.
Today even the rain-forests of South America and Afrika are being cut
down, rethlessly for wood, agriculture and animal husbandry, at such an
alarmingly fast rate that environmentalists are very worried and crying
themselves hoarse still, the floodgate of devastation is far from being shut.
Artificial Fish-breeding and Damage
to endemic genepool
e. Here is another aspect of biological pollution. This is fish culture
and gene pool. Recently techniques for fish culture have been vastly
improved. Fishery biologists have taught the fish farmers how to inject
the extract from pituitary glands to female fishes in order to induce them
to spawn in such waters where normally they would not spawn. Prof.
Hiralal Chaudhuri of Kolkata (1959), has made a significant contribution
towards this. This and other associated improvements in fish culture,
have encouraged fishermen in countries like Japan, India and others to
begin commercial fish culture in artificial impoundments in coastal-waters
and inland shallow ponds in an ever increasing scale.
*Tasmanian wolf (Canis dingo), the only marsupial carnivores, of Australasian
region are eliminated by the immigrant sheep ranchers of Tasmania in late 1930s!
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f. While this is good news to housewives but this is also eliminating
the local fishes. Consequently today in Kolkata fish markets while the
cultured fishes are relatively cheap and abundant but the endemic (local)
small fishes which were dirt-cheap before have become rare and
expensive. Mostly their habitats have been taken over for artificial fish
culture.
Through the above way an omnimous consequence may follow.
Some of the exotic commercial fishes such as, Tilapia (Orechromis
niloticus) which have been imported from Afrika (Lake Victoria) are being
released in the ponds of West Bengal, India. Thus while Tilapia has added
to the list of relatively cheap fishes for kitchen, it is also eliminating most
of the local fishes. Unless India and particularly West Bengal takes
corrective measures immediately we are afraid, many of the endemic,
fishes may vanish for ever. This would be a positive loss to the local
ecosystem and to the endemic gene pool of the country and in the long
run for the world. Similar things are happening with the food grains.
Special vareities of rice and wheat are being imported from South
America and Manila. These require lot of fertiliser and water still farmers
are growing these, to the exclusion of local varieties, for quick profit.
Gradually indigenous varieties of rice and wheat are vanishing. These are
some of the deleterious effects of biological pollution. There are more.
(Fortunately, owing to the efforts of Dr. M.S. Swaminathan, F.R.S.,
Govt. of India has set up a gene bank for indegenous plants but no such
efforts have yet been initiated to protect the genes of endemic animals.)
If we think a bit we shall realise that at the root of most of the
biological pollution lies the explosive growth of human populations
during the last thousand years (Fig. I. 1) particularly since Industrial
Revolution. Only in India human population has grown five times during
the last century (Table IX. 1).
2.D. PSYCHOLOGICAL POLLUTANTS
As this is not the theme of this book, so we shall only touch upon this
most briefly. At the beginning of this chapter it has been proposed that
“any agent—chemical, physical, biological or cultural which interferes
with the normal rhythm of Nature is pollution”. By interference we
generally mean detriment. From this angle, there are a few psychological
situations a human being may be exposed to, which leads to the detriment
of his mind. These situations are psychological pollutants. Here are some
of the most obvious ones.
a. Intense Competition for Best Grades In School
Today in many countries particularly poorer countries like India,
(author is an Indian) a child is put to school as early as possible even
before he or she is three. At once the happy childhood vanishes. Every
2.D. Psychological
Pollutants
INDIA
PAKISTAN
BENGLADESH
Years
Population
(in millions)
Birth
(per 1000)
Death
(per 1000)
Growth
(%)
Population
(in millions)
Growth
(%)
Population
(in millions)
Growth
(%)
1911
1921
1931
1941
1951
1961
1971
1981
1991
2001
252
252
279
319
361
439
548
683
844
–
49
48
46
45
40
42
41
37
32
–
43
48
36
31
27
23
19
15
11
–
0.6
0.0
1.0
1.4
1.3
1.9
2.2
2.2
2.1
–
–
–
–
–
34
43
65
89
132
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
51
–
90
–
129
–
–
–
–
–
–
–
–
–
–
Comments
A considerable
portion increase
in population is
due to reduction
in child
mortality and
lack of desire
for family
planning
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Table IX.1.
POPULATIONS AND GROWTH RATES IN INDIAN SUB-CONTINENT DURING THE LAST CENTURY (INDIAN POPULATION
HOWEVER EXCLUDES THE INDIAN TERRITORIES OCCUPIED BY PAKISTAN AND CHINA).
FROM CENSUS DATA FROM INTERNATIONAL DATA BASE AND OTHER SOURCES
Ecology for Millions
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day the child faces grilling both at school and in home for more and more
marks in class tests. Nothing less than 90% will do. The child's position
must be within the top 10% of the class. His happy childhood is
shattered. Both in school as well at home the child is in front of either
books memorising or, note-books writing. Even the child's holidays are
booked for tuitions, endless tuitions—mathematics, painting, music,
swimming, dancing (and even cricket). On top of all these the child’s
parents are forever chiding him/her for not doing better, for getting less
mark than the best boy/girl of class and so on. Hearing such
uncomplimentary comments all the time, that he/she is dull, that he/she
has no ‘grey matter’ in brain, in life he/she is sure to be a failure etc., the
child is very likely to develop a warped personality. What a nightmarish
childhood they go through. Later at the age of 5 or 6 the child will have
to carry a huge school-bag which would weigh 3/4 kg. We are afraid
their backbones may develop defects.*
Intense Competition
in School
b. An unhappy and book-worm-like-childhood is unnatural and
any child who goes through this torture is very likely to suffer as an
adult. Many mothers instruct their their children not to share his/her tiffin
with any body else. How can a child taught so by mother can over be
selfless?
Children are encouraged to be selfish
c. Cultural Outlooks of Communities
Achievements and attitudes of a man result primarily from three
factors—genes, family environment and schooling, the latter two we shall
concern ourselves with.
d. Role of Family
In many families children hear their parents belittling people of other
communities such as, fair-skinned people against dark-skinned people,
Moslems against Jews, so called Brahmin Hindus against non-Brahmin
Hindus and so on. Rarely children hear of basic human values and dignity
of man. How can such a child ever grow into a fair minded person?
Role of Family
e. Role of Teachers and Curricula
Again in schools students are too busy in learning merely a few skills
which would enable them to earn lots of money only. They neither have
time nor allotted any time to learn to distinguish morals from immorals,
ethical from unethical, loyalties from disloyalties or meaning of
responsibility. Simply they do not know that “Man does not live by
Bread Alone”.
Many teachers neither teach properly nor show through personal
example that taking money without discharging obligation tantamounts to
stealing. A man's duty to nation and himself extends far beyond his
*Recently the British Medical Journal LENCET has reported that school bags of
children are too heavy for healthy growth of their backbones.
Role of Teacher
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Ecology for Millions
immediate needs and comforts, that he is a moral guardian of his
environment—animals, plants, forests, and all. It is time we realise that
the long time interest—of a country lies in the interest of other countries
as well.
It seems to us, lack of these awarenesses is the root cause of most of
the unhappinesses of human beings over the world today.
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Chapter X
Problems and Solutions
(Challenges and Rising to Them)
Topics
X. 1. Philosophy of Ecology
X. 2. An Overview of Ecology
X. 3. Problems that we have generated
X. 4. Solutions
X. 5. Reorganise Town-Planning
X. 6. Agriculture and Ecology
X. 7. Better Water-Management
X. 8. Eco-Politics
X. 9. World Bank and Population of Under-Developed Countries
X.10. Ecology, Education and Values
This page
intentionally left
blank
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CHAPTER X
PROBLEMS AND SOLUTIONS
(Challenges and Rising to Them)
1. PHILOSOPHY OF ECOLOGY
Before delving into the enviromental problems and their ecological
solutions, it is time we briefly state the philosophy of ecology.
*All living beings of the entire earth and their non-living
environments are inter-connected and inter-dependant. Damage in any
corner of earth affects every other corners of earth.
*Organic evolution over the ages, have resulted in occupation of all
the varieties of niches of entire earth, be it a dark cave or a blazing desert,
with plants and animals who are specifically adapted for each specific
niche.
*Competition and elimination of the unfit are natural and necessary
processes of life and evolution hence should not be interfered with by
human beings unless unavoidable.
*Recycling of all bio materials is vital for continuity of life.
*The bounty of Mother Earth is not for men alone but for all living
beings. All living beings—from men, to decomposers, have a claim on the
space and resources of Earth as each play a vital role in maintaining
harmony in ecosystem.
*Human beings being endowed with the unique capacity of learning,
thinking, communicating and writing have a special duty to ensure that
justice is done to all other living beings, be it a humble insect or a mighty
whale, be it a blade of grass or a mighty sequoia tree.
*Finally, happiness of Individuals lies in the happiness of All.
2. AN OVERVIEW OF ECOLOGY
This small book contains the basic ecological concepts and information in
very simple language, for people whose knowledge of science may be just
minimal. It is like an attempt to present Zoology to someone through a
tour of a zoological garden. I am not sure if I have succeeded in
explaining to the readers, or lost them midway owing to the poverty of my
english which is not my mother tongue, the complexities of the ecological
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Ecology for Millions
principles and the importance of leading our lives in an eco-friendly way.
I hope the better. So here is in brief the principal ecological concepts
introducid in this small book.
2.a.i. Men of ancient civilisations were aware of the need of maintaining
Nature so, the sages and priests of those days introduced certain social
customs and taboos to protect animals and plants. “Ecology” as a defined
branch of science with a name of its own appeared only in 1869 through
Ernst Haeckel (German) and the word “Ecosystem” in 1935 through A.G.
Tansley, (English). Thus began the march of Ecology as a separate
discipline of knowledge.
ii. Three most remarkable and charming early books of ecological
nature that could be recommended to all are:
(1) Darwin And The Beagle—Alan Moorehead, Penguin, 1971.
(2) Silent Spring—Rachel Carson, Houghton Mifflin, 1962.
(3) My Family and other Animals—Gerald Durrell,
Reading these will arouse curiosity of readers to our living environment.
iii. Simply speaking, Ecology is that branch of knowledge which
deals with the relationships that the living beings have with their nonliving environments and vice-versa. Being basically an applied science,
Ecology draws upon various relatively pure branches of science such as,
Zoology, Botany, Genetics, Physiology, Behaviour Science, Geography,
Chemistry etc. (Chapter I).
2.b.i. The smallest self-sustainign unit of Earth’s biosphere is called
Ecosystem. For example, a forest, a lake or a coral reef etc. All these are
self-sustaining and hence ecosystems; with only sunlight from outside
these can sustain themselves. The main components of an ecosystem are
two—the living beings or biotic components and the non-living or
abiotic components.
ii. Plants, animals, fungi, bacteria etc. form the bulk of the biotic
components and, soil, water, air and sunlight form the bulk of the abiotic
components of an ecosystem. Besides sunlight, which comes daily from
sun, all the other components are integral parts of the ecosystem. The
biotic component again are devided into three main categories—the green
plants—who manufacture food materials from simple inorganic
ingredients by using energy from sunlight, the animals who live on food
manufactured by green plants and the fungi, bacteria etc. who, after the
death of plants and animals break-down the biomaterials locked up into
their bodies into simple inorganic materials and return these to earth to be
picked up and recycled once again by plants and thus repeat the cycle of
life over and over again (Fig. X. 1) (Chapter II).
2.c.i. The ecological fact of recycling of nutrients from abiotic to the
biotic components of the ecosystem, and then again from biotic to the
abiotic and so on and on—one cycle succeedig another till the ecosystem
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Abiotic components
AUTOTROPHS
Biotic components
HETEROTROPHS
De
cay
Animals
Decay
DECOMPOSERS
Plants
Decay
HETEROTROPHS
Soil, water, air, light, etc.
Figure X.1 An ecosystem showing cycles of life death
and life again (schematic).
lasts, is somewhat analogous to the religious beliefs of reincarnation
(rebirth after death) which we find in many religious teachings. While the
ecological fact of recycling is discovered through painstaking research
and observations which can always be verified through experiments, the
religious beliefs however, seem to us, owe their origin to the dictates of
the religious leaders or powerful coteries who used these beliefs to control
the minds of their followers. The earlier one is fact-based while the latter
is faith-based.
ii. All the food that we eat, all the wood that we use, all the rubber
that goes into the production of tyres etc., all the coal and petroleum that
we burn to obtain power, heat and all the clothings that we wear etc. etc.
are either produced by plants or obtained from power stored in plants. As
a matter of fact all human activities of the entire world are mostly directly
or indirectly powered by plants and plant products. Successive eras of
human civilisation have been possible only through more and more
efficient use of plants and their produce. Only recently men are obtaining
power directly from sunlight through such devices as solar cells,
windmills, etc.
iii. Production of bio-materials by green plants is called primary
productivity, by herbivores as secondary productivity and by carnivores as
tertiary productivity and so on. A portion of the total primary production
of plants is used up by the plants themselves to keep them alive and
provide energy for their metabolic processes. The remaining portion is
available to all animals and human beings for their food and other uses.
iv. The total biomaterial produced by plants is called gross primary
productivity or G.P.P. and the surplus portion of G.P.P. which is available
to the consumers is called net primary productivity or N.P.P. Similarly
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Ecology for Millions
there are terms for secondary producers such as G.S.P. and N.S.P. and
so on. Also, not more than 2% of sunlight is used by plants to produce
all the biomaterials of the world.
v. The health of an ecosystem is directly correlated with the amount
or its G.P.P. (This however is an anthropocentric point of view; there are
ecosystems which by virtue of their locations are bound to be of low
productivity such as, open ocean desert, but these are not necessarily
unhealthy from the point of view of Nature).
vi. G.P.P. in time, through N.P.P. influences G.S.P. and so on. For
these reasons measurement of productivities is a very important yardstick
to an ecologist. From the point of view of G.P.P. biomes like rain-forest,
agricultural fields and coral reefs are highly productive ecosystems. An
estimate of the annual N.P.Ps and Standing Biomasses, per unit areas per
year of all ecosystems (i.e. all biomes-both natural and manmade), are
also given (Chapter III Table 1).
T
2.d. Sunlight is the source of energy for green plants. Powered by solar
energy, green plants manufacture food utilising simple inorganic nutrients.
As the world depends of biomaterials manufactured by green plants or
G.P.P., the wheel of life of the entire world rotates on green Plants and
sunlight. This passage of solar energy by stages, with gradual dissipation,
from plants through various animals i.e. herbivores to carnivores and so
on till it gets totally dissipated into the environment, is known as energy
circuit (Fig. X. 2.). The aim of all agriculturists is to increase the primary
productivity of their lands. The success of a civilisation begins here
(Chapter IV).
G
H
E
L
I
N
N
E
S
U
R
Pla
nts
G
Y
Herbivores
s
ivore
Carn
Nutrient pool
Figure X.2 The energy circuit of an ecosystem (schematic).
ia
ter
c
Ba
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247
2.e.i. The energy from sunlight, after being trapped by the plants,
gradually gets dissipated away as it passes from one stage to another i.e.
from plants to animals etc. and gets lost for ever into the environment,
The inorganic constituents of living bodies however do not share the same
fate. The materials which are picked up by plants during photosynthesis,
after passing through various stages instead of gettig dissipated into the
environment like energy from sunlight, are returned to their reservoir pools
i.e. abiotic environments to be picked up once again by plants to initiate a
new cycle of life. This means that while the energy picked up by plants
from sunlight is lost to the environment irrevocably, the inorganic
molecules however are recycled again and again. This repetitive back and
forth movements of inorganic materials from the bodies of living beings
through the door of decomposition into the world of non-living and then
reentry into the world of living through the door of photosynthesis is
bio-gee-chemical cycle (Fig. X. 3).
Plants
& anim
als
s
Bio
t
ic
com
pone
nt
A
So
wa
te
ot
ic
r
ne
nt
s
ion
ai
po
sit
nd
m
po
ra
co
De
co
m
il,
bi
Figure X.3 A geo-bio-chemical cycle (schematic).
Bact
eria
fungi of
Ph
ath
oto
De
syn
the
sis
Biotic components
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Ecology for Millions
ii. Each chemical has a specific pattern of pathway. The study of
these pathways and the rates at which these chemicals move from one
compartment into another and while doing so, how these pathways are
now-a-days being frequently disturbed through interferences by men
fueled by population explosion, froms an extremely challenging as well as
exciting area of modern ecological studies. (Chapter X.V).
2.f. Dfferent environments or ecosystems affect different species in
different ways. For instance, frogs and toads will prosper in humid places
while reptiles will find dry places better. Also, growth of a population (say
deers) will depend on availability of food and presence of competitors such
as, other herbivores and predators. Therefore factors which regulate the
growth of the the population of a species, the nature of the growth pattern
of a population (i.e. if ‘J’ shaped or ‘S’ shaped), the size of a population
that can be supportedly a particular habitat, and the carrying capacity of an
ecosystem for a species, etc., all require careful study and clear
understanding if, we want to nurture a balanced ecosystem (Chapter VI.).
2.g. No ecosystem can be made of single species population. Several
interacting and interdependant species populations go into making of a stable
self-sustaining ecosystem. (This is true for human societies as well). How
from a no-life situation, through gradual stages, a stable, self-sustaining
ecosystem is developed is a matter of great interest. These and also how
populations of different species, through their life activities support each
other and create a holstic* process are discussed in Chapter VIII.
X.2.h. The beauty of the living world lies in its infinite variety of colours,
activities, sizes and behaviour of its inhabitants. Every single individual is
an unique creation of God. An insect is, from its own background is no
less pretty and useful than a resplendent tiger in a semi-dry forest. This
reminds us of two poets who wrote:
“To see a World in a Grain of Sand
And a Heaven in a wild Flower
Hold Infinity in the palm of your hand
and Eternity in an hour”.
—William Blake
(Auguries of Innocence)
*Holistic : An approach to the study of things or a situation taking into account
all the possible variables; a totalistic approach. This is opposite of meristic approach
which considers only one situation or one aspect at a time.
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Such uniquenesses of each ecosystem and the roles these play in the
overall life-processes of Earth are discussed in brief in Chapter VII.
X.2.i. Finally we have devoted a full chapter to discuss as to how by
introducing receklessly anthropocentric features into ecosystems (i.e.
features which are useful to men only) such as, dumping of harmful
chemicals into rivers or lakes etc. or pulling down large tracts of virlin
forest to make way for ranches or plantations, we are gradually strangling
the normal functioning of many of them. Unless such interferences are
halted immediately or, regulated stringently so as to let the ecosystem
function once again normally, the future of our human race is dark indeed.
All these are presented in this chapter—chapter X.
3. PROBLEMS THAT WE HAVE CREATED
After this brief recapitulation of the basic principles of ecology, we shall
now make a survey of the major injuries we have already caused to our
Earth.
3.a. The first major injury that comes to our minds is the wanton cutting
down of trees and converting good forest lands into agricultural fields or
cattle ranches. To-day most countries of the world which includes India
and China do not have even 30% of their original forest covers. India has
only 23% of its lands covered with forests while U.S.A. has 30%, Canada
54% and Brazil 58%. (Some countries have even less). This is a terrible
tragedy. The Thar desert of Western India is man made. 2000 years ago
the Thar was a jungle—abode of lions Unless we are cautious now there
may be more tragedies ahead of us. Here is a small table summarisig the
benefits that we draw from a single good true in 50 years (Table X. 1).
(Data first given by Forest Research Institute, Dehra Dun, India in
early 20th Century)
Table X.1
BENEFITS WHICH ACCRUE FROM A TREE IN 50 YEARS (ESTIMATED LIFE)
Item
1.
2.
3.
4.
5.
6.
Monetary benefit ( in rupees)
Oxygen production
Fodder Production
Premention of soil Erosion and Moisture Retention
Control of Humidity and Temperature of Environment
Accommodation to other Living Beings
Green House Effect
(Cooling effect through absorption sunlight)
–
–
–
–
–
–
2,50,000
20,000
2,50,000
2,50,000
2,50,000
5,00,000
TOTAL
–
15,20,000
X.3.b.i. The second is hunting down of wild animals, some for trophies
and some for food. In British India, shooting tigers for trophies and deers
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Ecology for Millions
for meat—mostly for barbecue, was a status symbol to the British
officers and rich Indians who loved to copy them. Christian Zuber in his
thought provoking book ‘Animals in Danger’ (Barrons, New York, 1978)
has reported that the tiger population of India has crashed from 40,000 in
1920 to a mere 1,800 in 1972 (Fig. II.3, & Fig. V.7). This alarming
decline is not only due to deforestation but mostly for sports hunting and
for furriers—who make a lucrative trade in selling furs, flesh and bones
of tigers. Indian princes have also played no mean role in decimating tiger
population. “There have been ‘Maharajas’ who have boasted of holding
the world’s record for number of tigers they killed. Three of them
claimed to have killed 1,000 tigers apiece.” The British Officers were not
far behind. “There was hardly a British Officer in India who did take
back home a number of tiger and panthar pelts to brighten his home in
England.” After independence Government of India has established the
‘Corbett National Park’ in the Himalayan Foothills of Western India to
protect tigers and other animals. Jim Corbett was a renowned British
hunter who had a genuine love and respect for tigers and shot them only
to protect the distressed villagers of never for sport.
ii. Indian Forest Research Institute at Dehra Dun, set up in early
20th century, has done valuable works about forest trees and insects but
has not paid much attention towards conservation of forest animals. After
independence of India, when animal fur as a trophy became very
valuable, —poaching multiplied. At times this is done with the connivance
of the guardians of forest. Indian lions are gone, tigers are going and if
Indians do not wake up now may be even their splendid bird peacock will
go the same way.
3.c.i. The third is the unplanned growth of cities. A city is like a big boil
on the skin and the skin is the ecosystem. Just as blood from
surrounding areas rushes to a boil and the spot feels warmer similarly,
people rushes from surrounding areas to a city for a living. Eventually so
many congregate there that they literally make a city climate warmer than
the surrounding areas. Also, to make way for houses and roads hundreds
of thousands of trees are felled—adding to the heat load of towns.
ii. And just as poison from a boil gradually spreads into the whole
body, the environmental poisons generated by a city populace such as,
wastes, deforestations etc. gradually spread over the entire surrounding
areas ravaging the ecosystem. Kolkata the first amongst the four British
Indian cities and administrative centre of British India for nearly one
hundred and fifty years, is positively an ecological disaster. Kolkata has
polluted and silted the river Ganga, largely destroyed a jewel of Mangrove
forests - the Sundarbans, swallowed and still swallowing the invaluable
swamps in east of Kolkata and its roads, pavements and buildings all are
preventing the recharging the groundwater during monsoon and causing a
host of other ecological damages.
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iii. Job Charnock, a British Officer founded Kolkata in the
Eastern side of Ganga, —a predominantly alluvial region, more than three
centuries ago, as a trading post safe from the Maratha raiders from west
and attacks from Nabab Sirajabdulla from north. Mostly attackers would
come from west and so have to cross the river Ganga before attacking
Kolkata. Hence Charnock chose East side of Ganga for Kolkata and
placed his guns on the ramparts of fort William facing Ganga in west.
British even dug a ditch within Kolkata—the ‘Maratha Ditch’—to halt the
Marathas.
iv. This city of Kolkata on the delta of Ganga stands upon
millions of years’ deposit of clay and peat. One can still find soft peat
soil under about 10’ of clayey soil in Accra (Batanagar), near Kolkata.
This soft black peat burns like coal. But now-a-days due to inadequate
recharging during monsoons (explained earlier), the clayey soil of Kolkata
is gradually drying up and buildings are sinking. This is more in Salt Lake
area of Kolkata which is built up on swamps recently filled up with silt
from Ganga. Roadside trees are not getting enough water as the footpaths
are paved up upto the bases of the trees leaving no exposed soil for
rainwater to enter into soil. Trees are gradually dying. Planting and
maintainence of Kolkata’s trees are both unplanned and ecologically
unsound. A glance at table X. 1 will remind anybody about the harms of
cutting down a tree.
v. Disposal of wastes from cities is another ecological threat. The
current tendency of land fils is a hasty cure for shortage of city dwellings.
Long term consequences of such unrestricted use of garbage are generally
overlooked. Such attitude is hazardous. Garbage needs to be sorted out
before reuse. The poisonous chemicals with persistent texicity need to be
sorted out before garbage is used. Otherwise such texicants will
contaminate the groundwater and then many ills would follow. Only the
ecologically harmless portions of garbage may be used for landfill. Part of
garbage can be easily used for producing biogase and manures. In fact
disposal of to day's garbage needs proper techniques based on knowledge.
With use of scientific knowledge and modern managerial techniques the
disposal of city-garbage can easily become industries creating jobs as well
as giving revenue.
3.d. Arsenic in Well-Water. This is a man-made damage. How it is
caused is discussed earlier (II. 3.c). Only on 12.01.99 the WNVC, TV in
Virginia, U.S.A. reported in ‘Asian News’ that the wells set up in the hilly
regions of Bangladesh for drinking water, with WHO money, are showing
dangerously high levels of arsenic. Earlier when there was forest canopy
in the hills, this arsenic problem was not there. Now when the forests
have mostly been cut down and hence canopy gone, the rainwater without
getting a chance to enter the soil rushes off into the nearest river. soil
remains relatively dry. Hence Arsenic from lower layers come up and
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poisons the well-waters. Similar cases of arsenic in well-waters are
recently being reported from several places of West Bengal, India. (For
details pl. see earlier II). Arsenic in drinking water is causing serious
health problems.
3.e. Burning of Fossil Fuels (coal, oil etc.). Burning of fossil fuels
such as coal for thermal plants or cooking or room-heating and
petroleum products for automobiles, aircrafts, motor vessels, thermal
plants and factories etc. are pouring in a lot of CO2 into the atmosphere.
Green plants are not able to tackle this huge additional load of CO2 into
atmosphere, through photosynthesis. This is resuting in gradual rise of
CO2 content of atmosphere. Consequently there is rise in atmospheric
temperature. All these have already been discusses earlier (V. 3.15).
3.f. Explosive Rise in Human Population. Today this is the single
biggest challenge facing humanity. Presence of Man is extremely
destructive to any ecosystem. Also, higher the standard of living a man
has the more costly is he to the ecosystem. Generally vegetarians are
relatively cheaper to the ecosystem than the non-vegetarians and rich
people who are not only mostly non-vegetarians but also demand many
special items to maintian their high profile living. An acre of land may
produce 25 quintals of wheat per year but it is unlikely to produce more
than 2 quintals of beef per year as beef is a produce of secondary trophic
level. A modern educated person would require not only wheat but also,
beef, chicken, vegetables, tea, coffee, sugar, cheese, milk, wines, various
fruits, etc. all to eat plus car, T.V. friege, washing machine, computer,
books, air-conditioners and a host of other things such as variety of
clothings, furniture, carpets, quilts and a four or five roomed house. On
top of all these to ensure ‘quality of life’ a modern man must furnish his
house with some ‘cultural items’ such a paintings, sculptures, some
animal trophies etc. to remain ‘modern’ and socially acceptable.
Compared to such a ‘modern’ man as we commonly find in Europe or
North America a school teacher in an Indian village, who is by no means
uneducated, would need very little to meet his needs. Three simple
vegetarian meals a day and milk, a few pieces of simple furniture, three of
four sets of cotton dresses, a few books, a bycle and a two roomed
cottage, would perhaps satisfy most of his present day needs. But this
simple hardworking school teacher of India would soon demand more
when he knows that people of his profession in Europe and North
America are enjoying such lavish life-style. But will the Indian ecosystem
ever be able to provide all these to her one billion children? Not this
ecosystem; not this India. At least the present author can’t comprehend
how. According to the Stanford Biochemist H.R. Hulett the carrying
capacity of Earth for human beings living in U.S. standards is about 1
billion people (Ehrlich and Ehrlich, 1970, W.H. Freeman and Co., San
Francisco). Our numbers is already far above this. Except a few how
many countries of the world will ever be able to provide such facilities to
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Problems and Solutions
their all citizens? Here are a few facts gleaned from Table (VI. 2) showing
the land available in suqare metres per capita in some selected
countries. India has only 3400, Bangladesh 1150, and Gaza strip only 364
square metres of land per person. India has only 4% or world’s land while
17% of population. This is terrible state indeed. The luckier countries
have much more such as U.S.A. has 35,700, Brazil 52,600 and australia
has 333,000 square metres of land per person. In fact population rise puts
pressure on ecosystem in a two pronged way. One is the simple need of
food and clothings and the other is rise in expectations of people. Earlier
few thought of owning a car or friege or computer. To-day everybody
want these. So we repeat : POPULATION RISE IS THE SINGLE
BIGGEST CHALLENGE FACING TO-DAYS WORLD whatever else
‘pundits’ may opine. No country can avoid misery unless his population
rise is halted immediately. China is the only country who has understood
this ecological lesson and has put it into use. China has halted their
population rise and China progressing fast. Whereas Indians only talk but
do little. So they are lagging far behind.
3.g. Our Obligations to Animals and Plants. Don’t animals have right
to live in peace? Are they not as much children of God as as we are?
Have we forgotten the Biblical teachings through Noah’s arc? Don’t
animals and plants have as much claim to the milk of mother Earth as we
have? Who granted us the Homo sapiens the exclusive right to kill and
use each and every species of living beings be it a gignatic blue whale
(Balaenoptera sp.) or a royal Bengal Tiger (Panthera tigris) or a beautiful
monach butterfly (Danaus flexippus) or a shy earthworm (Pheretima
posthuma) or shady huge banyan tree (Ficus bengalensis) or just even the
blade of a grass (there are many many species of grasses). Just to suit
our convenience? Plants are mute and most animals voice we can't
interpret. But they feel and they weep just as we do. Sir Jagadish Chandra
Bose a plant biologist from Kolkata proved long ago that (Comparative
Electro-Physiology—1907, Longmans, Green) that plants, if hurt plants
do feel pain just as we do. My dog Jimmy was such a jolly fellow that
we could almost see him laughing while playing with us; In U.S.A. they
have animal courts and special laws to prevent cruelty to them. But what
about the rest? We firmly believe that every animal has as much right to
a chunk of space in Earth as we have. On the other hand the fact that
we human beings are endowed with superior mental faculties than plants
and animals, this enjoins us to act as the guardians of plants and animals
and not their killers. We must protect them from wanton destruction.
Every species of living being be it a plant or an animal must have some
space to live free from human intervention.
3.h. Our Obligations to our Children. Having enjoyed so much of the
generous bounties of mother Earth, we are beholden with the duty of
leaving mother Earth, as a better and more rich and more gorgeous place
to our children than in what state we found her. With vision and courage
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to act now and make suitable sacrifices which are not too much, it is still
possible to salvage mother Earth from further impoverishment and set her
on road to recovery. Eventually such actions will yield rich dividends for
all.
Now let us examine how our knowledge of Ecology can help us to
discharge such vital obligations.
4. SOLUTIONS
Just as we have attempted to crystallise the major ecological problems we
have created for our mother Earth, here we are proposing such curative
measures which, we firmly believe, if adopted now will solve these
serious problems to a great extent although may not entirely.
4.a. HALT POPULATION RISE
First halt population
rise and than
diminish population
size
This is the single most urgent task. First thing to do is to halt population
growth. Nobody to have more than two children irrespective of sex of the
child and second thing to do is to see that in future families become
mostly much smaller in size than now. The achievement of these would
need a multiproged approach. Both incentives and disincentives are
crucial. A incentive such as, cash award amounting to say, 3 to 6 months
average pay of a person who goes for family planning after two children
would very much induce most people to do so. As disincentives,
withdrawal of some facilities such as, pay increments or promotions or
trade licences or house loan, bank loans for crop, seeds, fertilisers etc.
would put adequate pressure to most people to restrict their family size to
two. As an additional incentive rewards may be doubled if one goes for
Family Planning after one child. Any Govt. who thinks such expensive
rewards as too costly for his exchequer is simply myopic. With a simple
personal computer any Govt. Officer can work out how much a Govt. has
to spend on education, health, housing, travel, job, old age pension etc.;
on a single person during his lifetime. If he does so he will surely find
that giving a one time reward to a person for not having more than two
children is much more profitable to the Govt. than the latter options.
Simply, in most countries there is not enough land for more human
beings. Family size is going to be crucial for prosperity of any country.
With world's highest female fertility (7.68) and shortest doubling time (10
years). citizens of Gaza strip are most likely to remain poverty-ridden.
(Table X. 2).
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255
Table X.2.
SOME SELECTED COUNTRIES OF THE WORLD WITH THEIR FEMALE FERTILITIES,
POPULATION GROWTH RATE AND EXPECTED DOUBLING TIME OF POPULATION;
ARRANGED IN A DESCENDING ORDER OF DOUBLING TIME*
WITH THE SHORTEST TIME AT THE TOP
Country
Gaza Strip
Afganistan
Iraq
Saudi Arabia
Syria
Nigeria
Nicaragua
Laos
Cambodia
Jordon
Nepal
Papua New Guinea
Pakistan
Malaysia
Rep. Of Congo
Tanzania
Kenya
Iran
Egypt
Mexico
Bangladesh
India
South Africa
Taiwan
China
U.S.A.
U.K.
Japan
Poland
Germany
Female Fertility
Population Growth Rate
Double Time (Yrs)
7.68
6.01
6.26
6.41
5.73
6.17
4.28
5.76
5.81
4.94
4.96
4.26
5.02
3.40
5.06
5.49
4.26
4.52
3.50
2.97
3.45
3.29
3.22
1.77
1.81
2.06
1.70
1.44
1.36
1.24
6.59
4.21
3.62
3.42
3.30
3.05
2.92
2.78
2.72
2.60
2.53
2.27
2.22
2.15
2.15
2.14
2.13
2.12
1.89
1.84
1.82
1.72
1.51
0.95
0.93
0.89
0.25
0.23
0.04
0.00
10
16
19
20
21
22
23
25
25
26
27
30
31
32
32
32
32
33
37
38
38
40
46
73
75
78
280
304
1750
–
*Note: Doubling Time: For getting doubling time a thumb rule is used. Seventy divided by percent growth rate per
year gives an approximate doubling time of a populations.
4.b. ROLE OF WORLD BANK, INTERNATIONAL MONETORY
FUND AND SUCH AID BODIES
World Bank, I.M.F., countries such as G-8 and other such aid
organisations and can play a very pivotal role in halting population
growths. All aids should be linked with family planning. Except shortterms humanitarian loans for catastrophes such as, cyclones, etc. all longterm loans must be linked with family planning. Any country which seeks
Link all Aids with
Family Planning
and Basic
Education
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Limit FemaleFertility to 2 only
Ecology for Millions
aids or loans from others must first introduce compulsory family planning
and basic education for all its citizens before the country becomes eligible
for loans. Population rise must be halted. There is no escape from family
planning unless we are happy to live in perpetual misery. Number of
children per couple must be restricted to two. (also see 4.a). Bigger
families than this must be effectively discouraged. Countries with high
female fertilities such as 7.68 (Gaza Strip); 6.41 (Saudi Arabia); 6.26
(Iraq); 6.17 (Nigeria); 5.81 (Cambodia); 5.49 (Tanzania); 4.52 (Iran);
5.02 (Pakistan); 4.96 (Nepal); 3.45 (Bangladesh); 3.29 (India); and similar
other countries are a type of population “atom bombs” ticking to explode
(Table X. 2.). The whole world is interconnected. Misery and terrorism
are sure to reach, sooner or later, other corners of earth which are free
from these now. The recent World Trade Towers destruction should be
an eye opener to all. Unless immediate as well as long term measures are
taken now, more such tragedies are likely to follow. Just as the effect of
a boil if left unattended will, effect the whole body, so is with human
populations. Poet Tagore very aptly said..................
*
*
*
*
*
*
A glance at the earlier Table (X. 2.) would, we hope convince most our
readers that countries with high female fertilities are rushing to the brink
of misery and also pulling the rest of the world down with them. Aid
without family planning is a sure recipe for breeding terrorism. Besides,
owing to corruption most of the International aids gets evaporated in the
pipe line leaving very little to reach the destinations. Some of the aid
money get siphoned off for arms-purchase from developed countries,
many of whom seem to willy nilly connive with these unethical practice.
Selling F16 fighter planes to such countries is sure bring more trouble and
not peace.
4.c. PROTECTION OF WATER SHED
Prevent Soil Erosion
and Desertification
c.i. Water from snow-melts and rains all run through mountains, hills and
valleys till these reach the rivers and finally the sea. From sea water rises
as evaporation to form clouds from which water comes down once again
on earth as snows and rains. This goes on year in and year out and the
process is called hydrologic cycle. When rain water flows through
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257
wooded water-sheds, a good deal of it gets absorbed in soil (by sponge
effect action) and recharges ground water and the aquifers. If, on the
other hand, the watershed is made bare owing to human activities such as,
deforestation, agriculture etc., the rain water quickly rushes away, carrying
away with it huge amount of valuable top soil, before enough of rain
water can penetrate the soil to recharge ground water and aquifers, Thus
monsoon washes off top-soil and causes extensive land slides, creates
gullies, silts up river beds and increase frequency and severity of floods.
In fact soil erosion puts the entire river valley system in jeopardy.
ii. Thus Soil Erosion is a very serious problem. It takes more than
thousand years to build up one inch topsil. But many places of earth are
loosing several inches of top soil owing to erosion. Soil loss through
erosion in Asia is highest in the whole World. Asia’s Forest cover is also
smallest. In India the vast valley of Chambal river is completely ruined by
soil erosion. Now the valley is full of ravines and scrub jungles and
hideout for outlaws. So the following steps are being proposed to protect
the watersheds and river valley systems not only of Asia but also for the
rest of the world.
Cover all bare
grounds with
vegatation
II. RESTRICT DESERTIFICATION
Over the years, man’s activities have greatly increased deserts and
westlands. Desert covers of Earth surface have increased from 9.4 to
23.3 percent and prime deep forests have decreased from 43.9 to 21.1
percent. The Southern region of Sahara desert and most of Thar desert
of India is man made. During the time of emperor Ashok the centre of
Thar was forest and abode of lions. Even to day Thar is increasing in size
and Sahara is advancing southward on a broad front at a rate of several
miles per year.
4.c.iv. PROTECT AND NURTURE THE FORESTS
Cutting down of trees must be halted immediately. This is to be taken on
war footing. In forests old trees which are long past their primes may be
cut down by timber merchants but only after permission from forest
officer and under strict supervision of him. Logging to be strictly
controlled and immediately followed with afforestation. Also the same
timber merchant must be made to plant four saplings of the same tree and
protect this till these grow to suitable height. He should also undertake to
repair the damage to the road environment that might be caused by treefelling and use of heavy vehicles to transport the logs. To ensure all these
the merchant must be made to deposit guarantee—money with the
Government.
Logging only on
Ecologically sound
basis
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4.c.v. REWARD AFFORESTATION
Each person to plant
some trees
Individuals who afforest on their own inclination, ought to be rewarded.
This will help greening countryside, reduce soil erosion, provide shelter
and food to birds and animals as well as provide an wonderful
opportunity of earning for elderly and retired villagers. The reward should
be handsome and quick to motivate people and also to be given only after
these plants have reached a certain height. Thus villagers on their own
would become guardians of forests. Penalty and reward both are
complimentary components of good administration.
4.c.vi. GRAZING AND TWIG PICKING IN PUBLIC LANDS
vi(a). Grazing of all domestic animals in public properties has to be
altogether stopped if necessary, by suitable enactments. Grazing loosens
the soil surface and thus facilitates washing away of the top soil during
monsoons. So grazing does considerable damage to the ecosystem as well
as afforestation endeavours. Further of the local domestic animals (with
some exceptions) most are of very poor quality and consumes a lot but
gives very little. So it seems prevention of grazing in public lands will do
three goods. (1) Reduce damage to ecosystem, (2) reduce soil erosion and
(3) encourage people to keep only high yielding domestic animals and buy
fodder for these. Financially keeping only high quality domestic animals
will be more profitable and at the same time keep the ecosystems healthy.
Holland is an example.
vi(b) Letting villagers to bring their cattle into the forests during day time,
must also be stoped forthwith, for the same reason. These cattle not only
denudes the forests of their nutrients but also creates too much
disturbance to forest animals who need privacy and silence for breeding.
We have seen in Mudumalai forests of South India, cattle are let into the
forests in the morning and taken out in the evening at about 4 p.m. Also
the villagers who accompany the cattle pick up twigs and leaves from the
forest floor to be used as fual. The combined activities of the cattle and
the villagers not only denude the forest of their vital nutrients but also
disturb the forest animals too much. Consequently the soil is
impoverished. Besides, the carpet of dead and decaying leaves on the soil
surface acts as a sponge and help the rain water to enter the soil and
recharge the aquifers. Without this protective carpet rain water will
quickly run down the forest floor to the nearest river carrying with it the
valuable top soil of forest as silt. Then more ills will follow.
vi.(c) Anybody who wants to see himself the harmful effect of grazing
on land will only have to do a simple experiment. Fence up a 10' × 10'
price of land which forms parts of the land which is grazed, with chicken
mesh so that no grazing, twig—picking leaf licking etc. take place. Let it
remain so just for one year. The adjacent land will remain semi-barren and
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the fenced up piece of land will look like forest in begining [Photo—
X.1.(a) & (b)].
vi.(d) Summing up. If grazing, twig picking, leaf picking etc. are stopped,
the problems of soil erosion will be 50% less if not 75% within just
couple of years. Soil erosion in many tropical and sub-tropical countries
such as India is man-made which is due to lack of knowledge and
indifference of the natives to the long term good of the ecosystem and
thus the country. The best way to help villagers or tribals who live in the
fringe of the forests or in pockets within forests is to employ them in the
service of the forests so that they have some income through forests and
at the same time their knowledge of forests can be tapped to protect
forests.
4.c.vii. STOP “SLASH AND BURN” CULTIVATION
The ‘slash and burn’ cultivation which is locally known as “Jhum
cultivation” in Eastern Indian hills is still practiced by some local tribals.
This is no longer ecologically viable. Population have increased and so
have “slash and burns”. On the other hand, such scars on valleys increase
soil, erosion, river silting and finally floods. The increasing ferocity of the
annual monsoon flood of river Brahmaputra is partly due to ‘Jhum’
cultivations. Government must stop this ill practice if necessary, by
compensating the tribals. This will be far cheaper than flood control.
4.c.viii. AGRICULTURE AND SOIL EROSION
Single biggest source of soil erosion, silting and flooding is agriculture.
Birth and death of many civilisations are caused by agriculture and grazing
by domestic animals. Civilizations of Persia, Mohenjodaro and Harappa all
were splendid agricultural civilization. Their demise, we believe, were
primarily caused by soil erosion and silting owing to extensive tilling of
soil for agriculture. The entire “fertile crescent”* is no longer fertile. To
prevent this malady every agriculturist must ensure that the run-off water
from his fields do not carry away top soil or silt. He should also stop
grazing or at least regulate it carefully so that no soil erosion takes place.
Soil erosion must be stopped or at least reduced considerably at all costs
otherwise more misery are sure to follow.
4.c.ix. DISCOURAGE SETTLEMENTS NEAR RIVER BANKS
ix.a. Human settlements near river banks are ecologically wrong for two
reasons. First such settlements mostly get washed away during monsoon
*“Fertile Crescent”: Crescent shaped agricultural region of the ancient Near East
beginning at the Mediterranean Sea and extending between the Tigris and Euphrates
rivers to the Persian Gulf.
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Human settlements
beyond 100 meters
of banks
Develope riverbanks as tree-lined
strands
Ecology for Millions
floods causing loss of life and property and headache for the
governments. Secondly, run off from such settlements carry away
additional top soil silting up the river beds further and generating more
severe floods in succeeding years. To reduce the extent of such calamities
we propose two corrective measures. First all human settlements should
allow a 50 to 100 mtrs. margin beyond the high water level of monson.
Depending upon the gradient of the water shed, a 50–100m margin should
give enough safety margin for monsoon floods. Secondly, all river banks
should be meticulously covered with greenery—trees or grasses. And no
grazing whatsoever should be permitted in river banks. Cutting or pruning
of trees can only be permitted under supervision of forest rangers or
similar competent authorities.
ix.b. River banks near cities are gifts of God. City fathers should convert
them into beautiful strands to be enjoyed by all and ruined by none.
Unfortunately in many U.D.C.s people look upon the river fronts as freefor-all and hence soon convert these into cess pools of dirt, squalor and
crime. The banks of river Ganga on Kolkata and Varanasi and the banks
of Jamuna of Delhi are good examples of such misuse. With good will
and determination river fronts or waterfronts (by the side of lakes) can be
assets. For example, Chicago is a big city of U.S.A. by the side of the
Lake Michigan. About 70 years ago the Chicago water front was nearly
in as bad shape as the Ganga water front of Kolkata to-day. But the then
city-fathers of Chicago resolved to change the situation. Result—to-day
the Chicago water front is a pride to Americans and the Kolkata waterfront is, we suspect, a shame to Kolkata. This poor state of affair of
Kolkata water front is man made and man must undo it. Recently
however one Park has been set up in by the side of Ganga at Kolkata.
But it is too little.
4.c.x. RECTIFY AGRICULTURAL PRACTICES
Agricultural practices of many countries need radical changes. Briefly the
followings are proposed.
Punctuate agricultural fields with
strips of forests
(a) First: The modern large farms are ecological disasters. Tilling
facilitates soil loss. Loose soil is either carried away with water or blown
away by wind. Large farms with their continuous tilled grounds causes
considerable soil loss which must be reduced. To achieve this all such
farms should maintain a ring of undisturbed forest land like a girdle
around them. Such a girdle of forest land would reduce considerably the
soil loss and harbour many insects, birds and other animals who would
help to check the agricultural pests and thus serve a dual purpose.
(b) Secondly, we believe large and continuous tracts of agricultural lands
have caused demise of many splendid animals. Lions of India, passenger
pegions and bisons of North America and Tasmaniam wolf (Canis dingo)
of Tasmania all are such victims of agriculture or animal husbandry. It is
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time to pause and think. Large tracts of monoculture are very eco-costly.
(c) Thirdly, Chemical fertilisers are causing havoc with ecosystems.
Eutrophication of rivers and lakes is bringing change in the profiles of
flora and fauna of soil, rivers and lakes (explained earlier V. 3.7). All these
result mostly from agricultural fertilisers. Developed countries are learning
fast and changing their agricultural practices but U.D.C.s like India seem
to be reluctant to learn. Generally it seems to us more use of nitrogen
fixing bacteria, compost, and such natural fertilising organisms such as
earthwarms would reduce the need of chemical fertilisers to a great
extent. Also alternate sowing of cereal crops with leguminous crops
(pulses) will help in maintaining soil fertility.
Replace chemical
fertilisers with biofertilisers
4.c.xi. NO MORE INCURSION ON FORESTS
(a) Within last seventy to eighty years most of the U.D.C.s have lost
between 30-50% of what their forest cover was in the beginning of 20th
Century. This loss is mostly due to rise in population of these countries.
(b) This population rise however is not due faster breeding as is
popularly believed but due to better medical care and use of insecticides
—both of which are contributions of Western science and partly due to
logging for richer countries who preferred to import cheap and good
wood from poor countries to save money as well as their forests. This is
still going on. For example, export of the beautiful Salwood (Shorea
robusta) of from Malayasia and Indonesia is still going on. Another
example is the plight of Sunderban in the Gangetic delta of India the
abode of India’s pride—Royal Bengal Tigers (Panthera tigirs). About 100
years ago Sundarbans was nearly double of its present size. To-day
Sunderbans is only 2585 sq. km. One single tiger, being the largest
carnivore positioned at the top of ecological pyramid, require about 50 sq.
km. of forests to provide it with food. So Sunderban of today can’t
support more than 50 or so tigers. 50 tigers is not enough for a healthy
population. Present day Sunderban is not big enough for tigers. Some
vigorous correstive measures are urgently needed if Indians want to save
their tigers and their pride.
(c) On top of this precarious situation it is being proposed by the state of
West Bengal of India to erect an atomic power station in Sunderban. If
tigers of Sunderban can not be saved we think it will be a day of shame
for not only Indians but entire humanity. The long term ecological
problems that result from atomic power plants are very well documented
in N.G.S. of July 2002. We have also discussed about the harms of this
projects earlier (IX. 2.B.1g.h.).
(d) Summing up, any further shrinkage of any forest land must be halted
at all costs. Fallow lands adjacent to the forests should be taken into the
forests. Small villages at the fringe of forests should be gradually added to
the forests by paying the villagers adequate compensation so that they can
Halt in Population
Rise will reduce
pressure on Forests
Enlarge
Sunderbans
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Enlarge Forests
wherever possible
Ecology for Millions
settle elsewhere and or, by employing the villagers in forest service.
Through vigorous ecotourism money can easily be raised for such
compensations. In fact forests and rivers are the life support system of
all countries. These must be protected and nurtured at all costs if we
want leave a better Mother Earth for our children.
4.c.xii. NURTURING NATURE IS PROFITABLE
Eco tourism will
save Forests
Let Forest Guardians be Co-owners
of Forests
Man Nature wisely
and sell forests’
produce
(a) Moneywise Forests, Lakes, Rivers and Coral reefs alll are revenue
yielding resources. Properly managed, all these will attract tourists. Visits
to forests, collections of specimens from forests, hunting when culling is
necessary, (as they do for deers in U.S.A. and elephants in Zambia,
Africa), fishing and boating in lakes, collection of plant specimens for
medicine, all can yield revenues. If nature is managed wisely by well
trained and well meaning persons, using modern management techniques,
we have no doubt whatsoever that protection of the ecosystems will
generate assets for a country.
(b) As an incentive the guardians of forests should be allowed to share a
part of the revenue from forests. If this is done immediately the forests,
will become assets. Well managed “Safaries” are very profitable. Example
—African reserve forests. Much of a reserve depends upon the planners
and executors. Here are two examples.
Once myself with family spent a day in Jaldapara Reserve Forest in
North Bengal, India. I felt the forest is poor and animals are too shy for
a reserve forest. Here animals should fear no harm from humans. Their
rarity and shyness was certainly not healthy. The second are the reserve
forests in Tamilnadu and Karnataka states of South India. There are herds
of elephants and stands of sandal wood trees (costliest wood and used
only for religious purposes). A person—Birappan—a fugitive from law
with his gang has made these forests his abode for the last 20 years or
so. He is killing elephants for tasks and cutting down trees of sandal
wood for the last 20 years or so without caring for law. He defied the
Govt., killed several forest guards and some police efficers including a
few senior ones. It is believed that he has made at least 1000 million
rupees, if not more, through these illegal operations. Recently he has
abducted a very popular film star and asked a ransom for his freedom
making absurd demands from the State Govts. of Tamilnadu and
Karnataka. It defies common sense to concieve how such a brigand can
successfully defy law for a such a long time.
Profitability or liability of Nature depends exclusively upon the
wisdom and will of people and Government.
4.d. INTERCONNECT RESERVES : CORRIDORS
(a) Unlike plants animals move. In fact they need to move. Passports and
Visas are not for them. Some animals produce offstrings in one part of
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Problems and Solutions
the globe while they forage and grow to maturity in another part of the
globe. The two areas may be thousands of miles apart. Birds from Siberia
fly to India during winter to bred [Fig. 4. d.(a)] Eels spawn in the sargaso
sea while, the elvers, (eel larvae) grow in Atlantic and English rivers (Fig.
VI.22) near Florida, Marine turtles, whales, salmons and many other
species regularly travel thousands of miles between breeding grounds and
growing arenas. African wildebests and Alaskan moose both travel
hundreds of miles in search of food and favourable climate.
(b) Similarly animals in reserve forests need to migrate in search of food
or good weather or breeding grounds. To facilitate such migrations all
forest reserves, as far as possible, should have corridors connecting each
other. Inconnecting corridors would not only help in survival but also help
in the admixture of genes and thus ensure the health of a population.
Predators are great travellers. Tigers and lions easily travel 20 to 40 miles
in a single night. Elephants have to travel even more. Many Afrikan
highways are laid along the elephant tracks, as these have best gradients.
Most Indian reserves for elephants are too small for their seasonal
migration. So frequently these stray into human habitations. Corridors
between reserves will help the seasonal migrations of animals and flow of
genes. Also as far as possible these corridors should be from north to
south to facilitate summer—winter movements.
263
Need of Corridors
between Reserves
Corridors would
facilitate GeneAdmixture, so
species vigour
4.e. RECYCLE GARBAGE
Many of the items we use in our daily lives are recyclable. For example,
paper, plastic, wood, metals, glass, and ceremics all are reusable (after due
processing). The food wastes can be used to generate biogas and
fertilizers. Much of our own resources can be saved by recycling and the
environment will remain cleaner. Except North America, European
countries and Japan, it seems to us most countries are still not practicing
good recycling methods. In many countries of Indian sub-continent,
recycling is done genreally by ragpickers. The ragpickers only pick up
plastic items, papers and scrap metals. The rest of the garbage is used by
estate developers for filling up swamps to build houses on them. This is a
very dangerous practice. Many poisonous chemicals thus get released into
soil. Bioproducts are not available for power generation. Recyclable items,
glass and ceremic are denied recycling. Also indiscriminate feeling up of
swamps prevents recharging of water bearing strata of soil and thus
increase severity of summer drots.
4.f. DISPOSAL OF HAZARDOUS CHEMICALS
(a) Presently hazardous chemicals in usage are of six broad catagories.
First the fertilizers, second the insecticides, third the detergents, fourth
the industrial effluents, fifth burning of fossil fuels and lastly or sixth the
radio-isotopes. To render each one harmless needs more research to find
Many merits of
Recycling
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Ecology for Millions
out how long each of such items remain toxic in nature, what happens
when their breakdown-products interact with other chemicals in nature
and the effect of these chemicals and their breakdown product on other
non-target living beings. A few examples would elucidate some of these
points.
(b) DDT in human bodies: DDT (Dichloro-diphenyl-trichloroethane) a
chlorinated hydrocarbon is a powerful insecticide. This has been used
very extensively all over the world for mosquito control since World
War II. DDT is very powerful and at the same time a very durable
insecticide. Fifty percent of DDT sprayed in a field may be found in it 10
years later. The other half may not be detoxified—it may only have gone
elsewhere. There is another problem. DDE biologically active breakdown
product of DDT is virtually immortal. As DDT is so durable, its
concentration rises as it moves up through the food chain—from grass to
herbivores and finally to carnivores (a process known as biological
magnification which has been explained earlier). The permissible level of
DDT in cows milk set by Federal Department of Agriculture (F.D.A.),
U.S.A. is only 0.05 ppm. But around mid-sixties the level of DDT found
in human body fat in different countries was much higher (Table V. 3).
DDT reduces bird-population in nature. In the next example the
negative effect of DDT on ecosystem is more vividly demonstrated. DDT
interferes with the birds' ability to metabolise calcium. So the birds lay
very thin shelled eggs. Such thin shelled eggs are easily crushed by the
weight of the nesting parents. So the bird population drops. Populations
of fish eating birds such as, peregrine falcon, brown pelican, Bermuda
petrol all dropped due to their thin egg cells. Nesting failures amongst the
bald egales almost anihilated this species. Bald eagle (Haliacetus
leucocephalus) is the National Bird of U.S.A. (for more pl. see V).
Fortunately timely reduction and complete stoppage of use DDT saved
these birds from extinction.
(c) In this context Carson’s crusade in already mentioned (IX. 2.A.c).
Here we shall add a bit more. Rachael Carson (1907-64), editor for U.S.
Fish and wildlife Service published a striking book in 1962 “Silent Spring”
where she clearly stated that “The chemical barrage, as cruel a weapon as
a caveman’s club, has been hurled against the fabric of life”. Immediately
the manufacturers of chemical pesticides challenged her opinion; but
gradually she was proved correct till in 1976 the XV Int. Cong. of
Entomology firmly rejected the widespread use of broad spectrum and
persistant pesticides in favour of an integrated post management approach.
Carson’s first book, ‘The Sea Around Us’ was a best seller. In 1952 she
resigned her job to write full time. Then came in 1962 ‘The Silent
Spring’. In 1964 she succumbed to cancer.
(d) In 1980, India began manufacture of a very powerful toxin methyl
isocyanate (MIC) at Bhopal in a factory owned by Union Carbide of
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265
U.S.A. Methyl isocyanate is used to make ‘Sevin’* (Carbaryl) a very
powerful pesticide effective against more than 100 insect pests. In 1984,
on December 3, for reasons not yet clear, MIC from one of the three
storage tanks (of 40 tonnes capacity each), leaked out. Safety devices
failed. “Within days and with no known treatment or antidote, MIC
mained more than 1,00,000 people and killed 2500 making Bhopal
accident the worst industrial accident ever” (Brewer, p. 468). The victims
are still suffering.
Bhopal accident
(e) Letting industrial effluents go into the water systems (rivers and
lakes) or air is another source of danger. There are many examples. Here
are only two. Only a few months ago fishes of a river Churni, a small
river—about 50 miles North East of Kolkata, India, died. On enquiry it
was found that effluents from a paper mill entered Churni and caused the
death of fishes. The other is C F C and Ozone. C F C or Chloro-flurocarbon is extensively used in refrigeration. When this leaks out it goes
into the upper atmosphere, interacts with Ozone and destroys it. Now,
presence of Ozone in upper atmosphere is very important for living
beings. Ultra violet rays, a component of solar radiation, is lethal to living
beings. Ozone layer of upper atmosphere cuts it off and thus greatly
benefits living beings. If Ozone layer is destroyed due to C F C, “Ozone—
holes” are created in places of upper atmosphere. Already some Ozone
holes are created in the polar regions and harmful effects on living beings
of those areas are being noticed.
Industrial Affluents
(f) Another extremely problematic area of disposal is radio-active
substances. We already know of the horrendous effects of atom bombs
through Hiroshima. and Nagasaki. Also the serious consequences of
failure of an atomic reactor at Chernobyl, as yet remain unknown to us. A
few months ago ‘Kursk’ a Russian nuclear submarine sunk off North of
Norway—in Barents sea with 118 men and officers on board. All these
are very worrying indeed.
(g) All these, from DDT to nuclear submarines—all are very ominous
warnings for humanity. We think all nations ought to do the followings.
Review carefully the process of manufacturing, storage, use and
detoxification and decomposition of all items manufactured in factories.
Medidincs, fertilisers, pesticides, plastics and radio-isotopes—none should
escape srcutiny. Stop manufacture, storage and use of atom bombs and
similar mass destructive weapons. Halt erection of any atomic power
plant till we can ensure complete safety for the ecosystem. United Nations
should take this up as one of their priorities. Otherwise cleanup operations
would be very expensive (Nat. Geog. Soc. July, 2002), if not painful and
hazardous.
*Trade name given by Union Carbide.
Radio-isotopes
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Ecology for Millions
X.5. REORGANISE TOWN—PLANNING
5.a. Towns are generally children of powerful economic interests. Rarely
a town is planned keeping in mind the needs and health of its future
growing citizenry. For example, Kolkata was founded by Mr. Job
Charnock—an officer of East India Company as a trading centre
protected from the periodic forages of Marathas and Nawab Sirajadoulla's
soldiers. Thus initial aim was to pick up the merchandise from Eastern
India at cheap rates and without trouble and sell those at high rates in
England. East India Company saw to it that their English officers and
staff can live in decent surroundings. The local people were allowed to
stay in the fringe of this English people’s Colony and manage as best as
they could.
Kolkata’s owes
5.b. This is the overall history of most of the Indian modern towns which
grew up with the English. Thus grew Chennai, thus grew Mumbai.
Amongst the modern big town of India only Jamshedpur and Chandigarh
are planned from the beginning. As as result of all these life in most of
Indian cities and, I believe, in other U.D.C.s as well is very trying. Houses
are very conjested, car parking very difficult and road traffic very slow.
During office days one takes one hour to travel only 10 km. Roads are
very narrow and footpaths are mostly occupied by hawkers. Schools,
hospitals, and educational facilities mostly are both inadequate and or poor.
Few parks which are left are mostly bereft of lawn and trees and are now
being constantly used for Trade Fair or nibbled at by Government.
Children have no place to play and olds have no place to stroll or sit
upon. Now in order to widen the roads they are pulling down even the
shady trees which the earlier city-planers planted. (Trees absorb about
40-45% of incumbent sun’s rays). So soon in summer Kolkata will
become hotter.
Stagnant House
Rent and
Corruption
5.c. Stagnant house-rent is another bottleneck. In Kolkata house owners
can’t raise the rents nor can evict the tenants—both of which required
lengthy and costly legal procedures, which few can afford. With the result
the tenants are paying rents which are 1/10th to 1/50th of the current
rents. This has resulted in corruption in various facets.
5.d. So vigorous town planning is urgently needed. Towns must be
planned for future—remembering the mistakes of the past and sufferings
of the present. Followings are some suggestions. These however are
based on Kolkata which is the present authors home town. No city
should become a megacity. From an ecological point of view 10 million
seems to be the upper limit to which a city can grow. Just as a little bit
of increase in radius leads to manifold increase in circumference and in a
similar way, a little a bit of increase in population of a city beyond healthy
level results in various managerial as well as ecological and technological
problems. Human beings are not robots; they need a proper psychological
environment to grow in a healthy way. In houses adequate space should
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Problems and Solutions
be available per person as well as parking facilities for cars etc. Too
many people living in small spaces should be discouraged, by law if
necessary. High rise buildings are not always ecologically sound. It seems
for residential houses a maximum of five and for office upto ten stories
should be the upper limits. Roads should be wider (minimum three lanes),
with wide footpaths all of which should be laced with turf for rain water
to enter into soil, and trees at least on one side. Most of the rain water of
Towns/cities should be allowed to percolate into the city soil so that
aquifers become recharged during monsoon. No stalls should be permitted
on foothpaths. There must be adequate car parks in all public places such
as markets, offices, sports ground, parks, strands etc.. Target space should
be one car for every fourth person. If necessary under- ground car-parks
and wherever unavoidable, multistory above ground car parks ahould be
constructed. Very soon every family will own one car if not two. City
planners should brace themselves up for these urgent tasks.
5.e. Parking car in New Market area of Kolkata is a nightmare. This
should have never been allowed. If all the existing municipal markets of
Kolkata can be converted into 10 storey shopping malls with 2-4 storey
undergrounds car parks and if under all large tanks 2-4 storey car parks
are constructed, present car parking problems will largely vanish.
5.f. Sewerage and garbage disposal is most primitive in most of the
U.D.C, cities and towns. In cities in tropical and subtropical regions
where heavy monsoon rains are not uncommon, sewerage should be
adequate for such exigencies. Kolkata’s chronic water logging in
monsoon is a glaring example of inadequacy in planning and execution.
Such things should end. Garbage should be presorted at the point of its
generation and then put to reuse. This does not need any import of
technology only needs will and consciousness of the citizenry.
5.g. Rent laws of many cities particularly Kolkata, are very primitive.
While a landlord is not permitted to increase the rent (which might be his
livelihood) of his house except going through long-drawn and expensive
legal proceedings which may take years and a fortune to settle but a
vendor of tea in footpath can raise with immunity the price of his cup of
tea every three or four months. Hotel owners including those owned by
Govt. can raise their tariff almost every year. As a matter of fact
everybody can raise the price of his /her merchandise but not the
landlord. This is as if to be a landlord is a crime. One fails to understand
the logic behind this system. If I.T.D.C. (Indian Tourism Development
Corporation) can raise room rents of his hotels why can't the landlord
for the rooms of his house? It seems the grand intention of such laws is
to protect the interest of the middle class (a very hazy concept anyway).
But the result do not seem to be so. All these should end. New rent laws
should be enacted with justice for all and progress of the country in
mind.
267
Eco-Friendly Town
Planning: A few
Suggestions
10 storey shopping
malls and car parks
under markets and
tanks
Sewarage and
Garbage
Rent Laws vs. Hotel
Tariffs
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268
Parks with trees
and tanks
Tree line
Boulevards
Factories in Cities
Floating Population
of a City
Pay and Use
Facilities
Ecology for Millions
5.h. There should be plenty of open space in a city. Parks, lakes,
canals, gardens and sports fields all should be in plenty. Every child
should have access to a park within at least half a kilometre of his/her
residence. Cities like Kolkata, Varanasi, Allahabad and Delhi are blessed.
They are situated on river banks which are such natural assets. If the
strands are developed properly these could be beauty spots of a city. In
no circumstances a park should be viewed by politicians as a no man’s
land ready for grabbing. Calcutta maiddan has already been nibbled at in
many places in this way. These should never happen again. Parks are like
sacred social temples—meeting ground for all. Nobody should fracture
them. Like the body a Cheetah a city need to have plenty of green spots
i.e. parks. These parks should have tanks, play grounds and trees. Parks
with trees and tree-lined boulvards will not only provide shades to people
and roosts for birds, trees also produce oxygen—a vital requirement for
all living beings. Trees also keep a place cool by absorbing 40% of
sunlight. Similarly large tanks with some land around these as watersheds
will act as injection points to recharge aquifers with rainwater.
5.i. A city should never have any factory which produces harmful
affluents. These should be located far from the cities with adequate
protection for environment. Modernisation of rent-control law is revelent
even from this angle as well. Sometimes it is found that the grandfather
who was the original tenant used the house for residence but the
grandson has converted the house into a factory—perhaps a tannery. The
present landlord stands as an helpless onlooker.
5.j. Cities in U.D.C.s tend to collect a considerable size of floating
population. These people stay in city virtually free of cost. They sleep free
of cost on pavements, use parks and river-banks for answering calls of
nature, use roadside water taps for taking baths and washing clothes and
for running footpath restaurants. Virtually except buying food they spend
no money for living in a city like Kolkata. All of them earn—husband,
wife, children all—and send thousands of rupees every month to their
homes. Many own lucrative businesses right on the footpaths of busy
commercial centres and earn much better than many tax paying job
holders. Some of them owns cows and goats etc. which roam and feed
free in the “maidan” of Kolkata and give milk or meat to their owners to
make money. Besides food these people perhaps spend nothing more to
stay and earn in Kolkata. But the tax payers are bearing their burden. This
reminds us of Charles Dickens’ portrayal of London night during his time.
Are we still living at that age?
5.k. All these must be put an end to. Footpaths should not be used for
sleeping in night. Night bunks should be provided for by Government on
a fee. Roadside taps should only be used for drinking water and not for
bathing, washing and running tea stalls or food stalls. For such purposes
special paytaps should be arranged. For answering calls of nature
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Problems and Solutions
269
frequent pay and use public toilets should be installed. All citizens i.e.
people who live and earn in a city should pay for the city facilities
they enjoy. Getting things free spoils people’s character and in the long
term even the nation is affected.
5.l. Many of the city features of to-day can easily give dividends. Fishing
and boating in lakes can be charged for. Canals can serve as roadways
and also provide for fishing. These will be economically profitable and
reduce conjestion on roads and traffic fumes.
5.m. Need for public places for meetings: It seems all good cities and
towns should have several large open spaces—such as large fields, for
lectures by anybody. Police permission or intervention is undesirable as
long as the speaker does not encourage violence. Such places for airing
one’s views openly lets the steam out of a person and thus in the long run
helps all.
Canals as Roads
Lecture Arenas
X.6. AGRICULTURE AND ECOLOGY
6.a. One of the aims of Ecology is to find out how we can encourage one
species and discourage another. So aim the agriculturists. The agriculturists
however depend more upon artificial inputs such as, fertilisers, pesticides,
and power tilling. The ecologists on the other hand tend to exploit more of
biological principles such as competition, symbiosis etc. While the first are
environment costly the latter are environment friendly. Here are some
suggestions based on the latter approach.
India an U.D.C. is already producing enough food for its own
citizens. Based on current information, Indians have 97.5 kg of cereals
available per person per year (Table—X.3.) 97.5 kg. of cereals per year
for a person is certainly more than adequate as, besides cereals there are
other items which go into the dinner plate of people. The following
points/view presented here based on the above table and information from
earlier chapters.
Table X.3
ANNUAL PRODUCTION OF CEREALS IN INDIA AND CEREALS
AVAILABLE PER CAPITA PER YEAR. (BASED ON DATA OF 1999)
Annual Production
(Ton)
Population
(Millions)
Available per capita
(gross)
Less 25% as wastage
from insects, rats etc.
Available per capita
(Net)
130 million
1000 million
130 Kg.
97.5 million
97.5 Kg.
6.b. Based on the above data on India, it can be safely suggested that no
more forests need be felled in India to make way for agriculture, or
pastures or plantations.
Halt Deforestation
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270
Fourth Phase:
Phase of Genetic
Engineering
Bio-garden
Vegetarianism is
ecofriendly and
more healthy
Ecology for Millions
6.c. As per the history of human civilisation world is now at the
doorstep of fourth cultural phase. The earliest was the phase of
hunters and food gatherers; next came the phase of herdsmen and the
third is the current phase—the phase of agriculturists. Now mankind is
poised at the threshold of the next phase—the phase of genetic
engineering i.e. agriculturists of genetically engineered plants. At each
phase food production per acre rose broadly ten fold. So did the human
population (Fig. I.1). Now if both U.D.C. and D.C.s use genetically
engineered seeds or clones only, the production of food will rise so much
that the world will literally float on “milk and honey”. At the same time we
must put an end to any further rise of human population sparing no costs.
Soon after stabilising population growth we should aim at a gradual
reduction of population all over the world (save perhaps a few countries
such as Australia). Then we shall easily be able to return some lands to
forests. More forests will result in less soil erosion and more space for
flora and fauna to occupy and all to enjoy.
6.d. Need of bio-gardens. As more and more genetically engineered
seeds and clones will go into agriculture and animal husbandary, more and
more native plants and animals will tend to vanish. That will be
hazardous. Each species has evolved over hundreds of thousands of years
to fit a particular niche. To eradicate any of them just to make way for our
immediate needs will be ecologically costly and will also cause irreperable
damage to Nature. We are custodians of Nature and not a band of
usurpers. In order to prevent this risk all countries should join hands and
create extensive bio-gardens all over the world—both on land and sea,
spread over thousands of square kilometres apiece. In these bio-gardens
all endemic varieties and species of plants and animals will be left in peace
to breed and survive as per the laws of Nature. As far as possible these
should be interconnected three corridors.
6.e. Need for vegetarianism: From our knowledge of ecology we now
know that weight for weight, meat production requires approximately ten
times more land than food grains. Therefore the more men adopt
vegetarian food habits the less will be our need for land for agriculture
and pasture. The preponderence of vegetarians amongst the Indians is an
eco-friendly habit. We now know that as a result of ‘biological
magnification’ (please refer V), the various chemicals we use to-day in
agriculture are becoming increasingly concentrated in our bodies as these
move from plants to herbivores and from them to carnivores, (ex. DDT
in human body, Table V. 3.). Very likely some of these unwanted guests
into our bodies are the causes of some of our present-day ailments. For
example, it has been proved that the virility of human males is going
down as the use of chemicals in our daily lives are going up. It seems
therefore both on the count of demand for land and on the count of
concentration of poisonous chemicals into our bodies, vegetarianism is a
better option.
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Problems and Solutions
271
6.f. Should we eliminate competition amongst humans?
Should human beings who are born with congenital defects be allowed to
reproduce uncontrolled and perpetuate those defects? Or, let the natural
process of competition and elimination of the unfit be allowed to prevail?
Most of the attitudes which are prevalent now seem to stem from hearts
than from heads. With more and more technology at our disposal, human
societies are becoming increasingly insulated from forces of Nature.
Nature tends to eliminate the weak and favour the fittest and thus
maintains species vigour. Are we not interfering too much with the
forces of nature?
Competition and elimination of the unfit
6.g. It seems it is time politicians, scientists, social scientists, doctors and
such people should take a hard look on this important issue of
reproduction by persons having congenital drawbacks. Now-a-days
owning to urge of family planning and availability of better medical care,
infants even with congenital defects mostly survive and can pass on their
defective genes to the society and thus perpetuate it. It is time the
aforesaid peer group should ponder on this grave issue and then give a
humane as well as logical advice to parents regarding the suitability of
their having children with serious genetical drawbacks, without infringing
however upon their basic human rights, on a case-by-case-basis. It is a
very contentious issue but still a beginning should be made.
Congenital draw
back and defects
X.7. BETTER WATER MANAGEMENT
7.a. Most of the underdeveoped countries receive a good deal of rain
water. However due to lack of knowledge and enterprise these countries
are not able to make much profit from this bounty of Nature. Mostly
rainfall is allowed to rush down the ground-surface to the nearest river or
lake after, a wet monsoon and giving only one seasonal crop and leaving
rest of the year more or less dry and unproductive. Using ecological
principles as guidelines and energy to act, much of the surplus water of
monsoon can be used much more effectively. First, some rainwater can
be stored into small above-ground tanks to be used as drinking water
throughout the year. This will solve arsenic problem. Secondly, part of
rainwater can be stored in suitable small earth impoundments or dug-out
ponds for irrigation during dry seasons. Thirdly, some rainwater need to
be allowed to seep into the soil to replenish the depletion of ground water
owing to irrigation wells and tube wells etc.
7.b. All the three above suggestions are neither economically costly nor
need hitech. UDCs can easily construct small earth/stone impoundments
in hilly areas or dig suitable ponds in flat lands. Local people can donate
some free labour and also sell the surplus earth thus dug out from the
pond. The seeping of rainwater into the soil can also be encouraged
easily. The roads and the footpaths can be thus paved that, rainwater
falling on these instead of rushing headlong to the nearest river or lake
Monsoon water and
its proper use
Revenue from
Water
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Ecology for Millions
through the sewers, will slowly seep into the soil through a turfed strip of
land by the side of roads and the rest would flow into a nearby lake
which will form part of park for the neighbourhood. Every town and city
should be dotted with such parks and lakes. From fishing, boating,
swimming and their orchards, a park can give good revenue. Further,
rewarding of individuals for afforestation in public lands and compulsory
afforestation for loggers will help increase the ground cover with trees
and recharging the aquifers. Grazing of domestic animals in public
properties should also be strictly regulated and charged for so that
saplings and ground cover of soil with vegetation is not disturbed.
All the three above suggesions if put into action will greatly ameliorate
the chronic water shortage problems of many UDCs without much cost.
These would neitheir need foreign aid nor hitech. Only will to act and use
of a little bit of ecological knowledge, are adequate.
X.8. ECO-POLITICS
Scientific Discoveries and Expansion of Western
Culture and Torpor
in Orient
8.a. Political decisions are most conducive when these are enmeshed and
strengthened with scientific discoveries and inventions. During 15th to 18
centuries a number of very important discoveries were made in West
European countries. Prince Henry the Navigator of Portugal (1394-1460)
established a School of Navigaton which made vast improvements in
techniques of navigation in sea. Sir Isac Newton in England (1642-1727)
and Wilhelm Leibniz of Germany (1646-1716) developed Calculus which
helped in astronomical calculations and navigation in sea. All branches of
Sciences underwent a spurt of growth. At that time the King of Portugal
commissioned several expeditions through sea to find an alternate sea
route to India—the fabled land of wealth. (The other known route was
through land which was dominated by Arabs). Bartolomeu Dias was sent
South. He arrived at Indies in 1447. Christopher Columbus sailed west
and arrived at a island of Bahama group, near America in 1942. Dom
Vasco da Gama arrived at Calicut of India in 1498. Later, Captain James
Cooke sailed on his now-famous circum-navigational voyage sailing,
“Endeavour”, and arrived at Australia, New Zealand and Tasmania during
1768-71 and hoisted flags of Gt. Britain on these vast areas. During that
period Sir Joseph Banks (1743-1820), a young, rich and Oxford trained
naturalist provided the outfit of Cook’s expedition and accompanied him.
On return to England Banks threw himself into a flurry of activities,
initiating steps to collect economic plants from all over the world and
introduce them in suitable countries. The then reigning monarch of
England patronised Banks. The famous Kew Botanic Gardens in London
is primarily a result of Banks’ endeavours. Similarly at that time Warren
Hastings—the first Governor General of India (1774-85) sent an
expedition to Tibet primarily collect and bring all plants/animals from
there, which are likely to be economically beneficial. Thus from 1500 till
1800 European civilisations spread out rapidly to the entire world and
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Problems and Solutions
273
through them a new global order emerged. Thus began exploitation of
Nature and spread of European culture in a global scale. During that
golden age of Europe, Orient was languishing in the glories of her past.
8.b. Ecology is a growing branch of science. Its main aim is to find out
the relationships of living beings including humans with their environment
and vice versa. Knowledge of ecology ought to be very relevant for
national planning. Unfortunately however, men in power particularly in
U.D.C.s mostly run after quick profit sometimes even by comprising longterm interests of their nations. To compound the problem further the so
called intellectuals of U.D.C.s tend to confine themselves with narrow
academics without trying honestly enough to make their knowledge and
skill useful to their countries. National decision-makers too rarely demand
their service and result oriented works. Gradually with time, such
intellectuals get distanced from society and her needs. Many Universities
in the Orient tend to remain—serene and aloof without much concern
about the needs of the society which supports them. Consequently, many
political decisions in the U.D.C.s are of ad hoc nature without using much
of science and consideration for long term interests of the countries and
ecological consequenses of such actions. Many of these motional interests
however can be easily identified if ecological principles are considered.
Here are some examples:
8.c. Selling out national resources most of which are of nonrenewable nature. It is an well established fact of ecology that when
watershed gets exposed owing to logging or agriculture etc. severe soil
erosion follows leading to many ills. Old regal sal trees (Shorea robusta)
of Malayasia are being cut down and exported. Most of these must be
more than hundred years old but are still healthy and having a diameter of
4 feet or so. These are being sold to rich countries for dollars apparently
without cosidering the severe ecological damages that is being caused to
the land. Malayasia’s beautiful forests along animal fauna all are going.
One has only to read a few pages of Alfred Russell Wallace’s travel
memories of Malaysia’s jungles to get a glimpse of its past beauties of
that region. It is a natiolnal tragedy for Malaysia whose ripple would soon
reach rest of the world. When the public will at last wake up it will be too
late. India is exporting her best iron ores from Balaidilla mines of Orissa,
with 80% iron, which is world’s best, for money. Mineral resources are
irreplacable, and one should be very very cautious about using up these.
In Congo valley of Africa they are cutting down lots of prime forests for
wood to make figurines for export or for decorated coffins. These are
ecologically very unsound practices. Many U.D.C.s are replete with such
mistakes. U.S.A. is carefully protecting per prime forests. Ecological
consciousness amongst the guardians of these UDCs could have
ameliorated many of such ills. The paws of Dollars are on the throats of
most UDCs.
Ecology and
National Planning
U.D.C.s are selling
out their wealth
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Gause’s Principle
and mixing of
human populations
Ecology for Millions
8.d. Governing without considering effects of population interaction/
( i.e. ignoring Gause's principle). Gause’s principle states clearly when
two populatios compete for the same resource, one who have slight edge
over the other will ultimately eliminate the later. For instance, when an
ethnic group of financially very smart people migrates amongst another
ethnic group of people, whose financial sense is not so keen, as the
immigrants; the native group will soon find themselves outwitted and
outmanouvored by the immigrants. The recent success of immigrants
from Gujarat. India, to U.S.A. is an example. Such immigrants have
captured a large share of the chain food shops and other businesses.
Similarly, the money market of Kolkata is by and large, gone into the
hands of people from other corners of India. The locals are outwitted.
Histories of human migration is replete with stories of such tragedies for
the locals and comedies for the immigrants. Again this is also an
ecological truth that the population intermix and gene interflow are
necessary to improve populations. Therefore powers that rule the
countries should ensure some amount of competition but not allow
complete elimination of one group by another so that, ultimately by slow
intermingling of populations all will benefit. Success of U.S.A. as a nation
seems to us, owes much to this slow admixture of various populations.
Afro-Amricans to day are as much an American as Euro-Americans are.
So to ensure survival of all communities in an area/state, government has
to allow provisions so that a relative weak comunity does not have to
face very stiff competition but at the same time is not entirely free of
competition. Such policy will ensure slow admixture and improvement of
all communities. Theocratic societies or countries who tend to discourage
presence of other communities amongst them usually with time
degenerate.
8.e. Demography and populations balance
Importance of
secularity
Demography, a branch of population ecology, clearly shows that the
nature of a population will be largly guided by size and nature of its prereproductive and reproductive populations, besides female fertility and
infant mortality. Short sighted politicians tend to keep their eyes off these
guidelines merely for the sake of winning elections. India is a good
example. One of her Former Prime Minister amended the Constitution of
India so as to let the Muslims have four wives at a time but not the nonMuslims. This discreminatory change in civil codes will ensure a faster
growth of Muslim population in India than Hindus. Presumably Late
Prime Minister did this unnatural thing to ensure Muslim votes so that he
can retain his position in Parliament. Two ills may follow such an
unsecular and ecologically unsound enactment. First: This will lead to
demographic imbalance—with percentage of Muslims in Indian population
perpetually rising against a perpetual drop in the percentage of nonMuslims. Secondly: The loyalty of Indian Muslim citizens will suffer from
doubt. Now both of these appear to be happening.
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Problems and Solutions
8.f. This is however not fair to the Muslim community. We are sure
some of them are as much loyal as any other Indian. Late Captain
Hanifuddin of Indian Army is an example. During the Kargil conflict
Captain Hanifuddin faught against Pakistan raiders, who were all Muslims,
with examplary courage and fortitude. He laid down his life to recapture
a strategic peak which the raiders sneaked up to during winter snowstorms. Befittingly India has renamed that peak as Hanifuddin peak.
Nevertheless, if any Government woos a particular section of a
cummunity for vote, at the cost of other sections, painful consequences
are bound to follow. Already such symptoms are becoming increasingly
conspicuous in India. Disregard to simple basic ecological principles by
men in power causes a lot of harm to a country and its ecosystem.
Considering all the above it seems to us that just as economists are
required for National Planning so are ecologists. Both are vital.
275
Need of Ecologists
in National Planning
X.9. WORLD BANK AND POPULATION OF
UNDER—DEVELOPED COUNTRIES
9.a. Most U.D.C.s are poor; their poverty however is largely man-made.
Interestingly, most of them are rich in natural resources. When these
countries achieved independence from their European rulers, they were
left in relative peace and with a strong administrative fabric. Unfortunately
however, when the ruled became rulers, most lost their sights. Instead of
guiding their young countries to higher levels education, family planning
and prosperity, most rulers, (with a few honourable exceptions), set their
targets on personal interests and vote banks. The inevitables followed.
Gradually these countries became riddled with corruption and burdened
with bigger and bigger debts from developed countries. These, coupled
with reduction in child mortalities and no serious effort for family
planning, soon led to explosive growth of populations. With a little
arithmatic and plain foresight the leaders could have easily guessed what
lies ahead and so could take correative measures. But this they did not.
Singapore is perhaps the only exception. Its leader had foresight and
courage to act. In spite of poverty and ethnic diversity to start with,
today Singapore stands with her head high in the comity of Nations.
9.b. India had 30 and Bangladesh (then East Pakistan) had 2 1/2 crore
people when they became indepemdemt in 1947. Now they have 100 and
10 crores respectively. Inevitably they are always at the door of World
Bank with beggars’ bowl. World Bank which is primarily nourished with
Developed Countries’s (D.C.) money is giving loans but hardly the right
advice. Instead of linking aids with population control, they are giving
aids for power generation, agriculture etc. These are only short term
solutions of some needs but the source of all problems—the rising
populations remains unattended. Availability of more power and food-aids
have, in a sense, become counterproductive to the U.D.C.s. Earlier infant
Over-population and
Corruption
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Ecology for Millions
mortality of most U.D.C.s. were very high. Besides frequent famines,
cholera, malaria, ptyphoid, small-pox etc. greatly checked the population
rise (Darwinian effects). Today the influence of these natural population
controls, owing to better medical facilities, are far less effective. Besides
the surplus populations U.D.C.s have no place to go and colonise as
D.C.s did earlier. Here we place some data from Harper Collins ATLAS
OF WORLD HISTORY, 1998. (page 208 & 209).
9.c. It has been estimated that in the 19th century the population of the
world expanded more rapidly than in any previous period, from about 900
million to 1600 million. (During the 20th century it was to grow four
times faster.) The population of Europe increased from 190 million to 423
million; at the same time, European peoples—the emigrants and their
descendants—settled in North and South America, South Africa, Australia,
New Zealand and Siberia, and the population of these regions grew from
5,670,000 to 200,000,000 between 1810 and 1910 of the three countries
which were the leading industrial states in 1914—the United Kingdom,
Germany and the United States—the population had increased nearly five
fold in the previous hundred years. The distribution of the world's
population at the beginning of the 20th century was estimated to be as
follows (again in millions): Europe 423, Asia 937, Africa 120, North and
South America 144 and Australia 6. Here is a map of the world
population movements from 1821 to 1910 ( Map. X. 1.).
Map X.1 Migration of human populations from 1821-1910.
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Problems and Solutions
9.d. Amongst the earlier leaders of the U.D.C.s Chairman Mao Tse Tung
of China was the only leader who had the right foresight. He insisted on
family planning and self-dependence. India never learnt this lesson from
China. To-day U.S.A. is flirting with China but frowning at India. China’s
atom bombs are O.K. with the D.C.s but India’s and Pakistan’s atom
bombs are not. (The author does not support any atom bombs—
whosoever may be the manufacturer or the owner. It is the partiality of
the D.Cs’ attitude that he is pointing out. This is not fair. Unfair actions
breed unfair reactions). So the U.D.C.s of today are comming more and
more under the economic domination of the D.C.s. and also the surplus
population of U.D.C.s of today has no such opportunity for large scale
migrations as the D.C.s had and still have. Unfortunately the U.D.C.s in
general, seem to be indifferent of this menacing problem. Their too little
land is shrinking further. Moreover some of their leaders even look upon
population rise as an aid to their vote-bank. Some seem to encourage
illegal immigration just for vote bank without caring for the horrendous
future they are laying the seeds of. These myopic policies appear to us as
a source of misery of most U.D.C.s. Only the Indian industrialist Late Mr.
J. R. D. Tata foresaw this problem and tried his best to convince the
rulers to pursue a more vigorous population control policy. But he failed.
According to the latest census (2001) West Bengal of India, now has
nearly 80 million people but only 88,752 sq. km. area. Can such a
overpopulated state ever be affluent and develop a balanced economy? So
is true of most of the other countries.
9.e. Another game the D.C.s appear to be playing and which the U.D.C.s
are not seeing through seem to be this. On flimsy excuses they are
encouraging U.D.C.s to split up and become smaller states. The game is
simple. A small state will remain permanently under the apron of D.C.s.
For themselves D.C.s have different policy. They are uniting and
becoming stronger. East and West Germany have become united and
European Economic Community with single currency have been formed.
Only recently EEC of 15 states have admitted 10 more states into their
fold and thus has become a mega-state of 25 members—virtually an
empire. Americans faught a civil was under the leadership of Late
President Abraham Lincoln to remain united; whereas India faught a small
civil war in 1946 to become devided. These two smaller countries, created
by splitting one country, (by the then British rulers), are bleeding since
then, whereas recently U.S.A and Canada has come under a single
protective canopy for defence.
9.f. Late Prime Minister Winston Churchill once said that he would like
to name the Second World War as the ‘Unnecessary War’ (Memories of
Second World War. Winston Churchill, 1948-65. In the same way I
would like to call the division of India into India and Pakistan in 1947 as
‘The Unnecessary Division’. Also, Churchill once said that the uniting all
the english speaking nations of the world under one banner, would be his
277
Oportunity of
migrations D.C.s
had and still have
Altitude of the D.C.s
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Ecology for Millions
greatest service to his country. The U.D.C.s in general, dont seem to
learn much lessons from history. The single biggest challenge to most of
the U.D.C.s of today is to halt the galloping rise of their population. And
another is to stop this fissiparous tendencies amongst their politicians and
local leaders and make them realise where lies their real good.
X.10. ECOLOGY, EDUCATION AND VALUES
10.a. To a nation a properly educated person is an asset and a wrongly
educated person is a liability. Violence is no way for fixing wrongs. The
people or organisations who are orchastrating such senseless destructions
and killings of the innocents as in World Trade Centre (11.09.2001), in
Bali Night Club, in a train in Madrid, or valley of Kashimir, or Moscow
and many other corners of the Earth , are doing more harm to their
causes than good. While a person like Mahatma Gandhi with his message
of universal love and non-violence, or Mother Teresa of Kolkata with her
kind hands extended to sufferers to any corner of the earth or charitable
organisation like Bharat Sevashram Sangha of Kolkata who always rush
to any spot of natural calamity with food and clothings or for that matter
International Red Cross, all are working as universal balm for humanity—
always trying to save a life and not to take a life.
Education and
Ethics
10.b. So for enduring peace and prosperity for future, all nations’ first
priority should be to educate their children in a proper way. Proper
education is a self-regulating and self-correcting device. When into the
young and impressionable minds of children the seeds of universal love,
honesty and fairplay are implanted by family and teachers, these take root
and stay put. Such children develop into useful and powerful adults.
Unfortunately, many countries particularly U.D.C.s are not allotting
enough money and thought for educating their future citizens. These
countries are content if the people are literate. But mere literacy is not
enough—not at all enough. The post-school education are mostly limited
to teaching the students only a few skills by using which they will be able
to earn a living. Most young people aim only at making money and more
money. Few seem to look beyond money and seek higher goals. Fewer
still seem to worry about moral values, loyalties, duties to nation and
obligation to Nature. The state of affairs in some countries are deplorable.
Some countries go even further. State fund is spend to teach students
specific religious creeds to the exclusion of all others. Some of these
creeds seem to teach their students about the superiority of one particular
religion and stress on the inferiority of others' and so look down on them.
Thus the seeds of dissention and hatred are sowed early in life.
10.c. Man does not live by bread alone. Therefore, besides teaching a
student a skill for a livelihood, which he must earn, he must also be made
conscious of the higher aims of human beings who are the supreme
creations of God. We submit that besides teaching a student a skill to
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Problems and Solutions
279
earn a livelihood, a student needs to be taught the duties of a Man to
Nature, to his Nation, to others who belong to Other Nations—as the
world is really a whole and one—(only artificially partitioned by politicians
for mean self-interests) and duties to his Family and Friends. The ultimate
goal of Man is the search of self-realisation and see that he brings joy,
happiness and prosperity to an ever widening circle of Humanity and
Nature.
10.d. While we strive on and on the road to progress, we shall commit
mistakes. But let not the mistakes be deterrents. As long as the intentions
are fair and honourable, we should admit the mistakes, rectify the course
and move on. We may be slow but still we shall progress. Philosophers
said “Wounds of Reason can be Healed by Reason Alone”. In the sanscrit
scripture ‘Vedas’ this attitude is very optly put through a terse phrase.
(“Halt Not, Move on, Move on”—Translation by author)
The twin vice of igorance and greed have caused considerable
damage to the health of our Mother Earth, still, all is not lost. If each one
of us read a little, think a little, and do a little for Her. Her health will
surely be restored. She will once again flower into Her many splendoured
beauty and humanity will truely enter the Garden of Eden.
A little knowledge of Ecology and its practice in life would form the
first step towards that goal.
Phitosophy and
aim of Life
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